Test: add space after test failure for visual clarity

[IanButterworth]

Small change. Currently sequential failures visually clump together.

Example failures

master

Pkg.precompile: Test Failed at /home/runner/work/Pkg.jl/Pkg.jl/test/api.jl:173
  Expression: length(broken_packages) == 1
   Evaluated: 0 == 1
Stacktrace:
 [1] macro expansion
   @ /opt/hostedtoolcache/julia/nightly/x64/share/julia/stdlib/v1.10/Test/src/Test.jl:477 [inlined]
 [2] (::Main.PkgTestsOuter.PkgTestsInner.APITests.var"#17#32")(tmp::String)
   @ Main.PkgTestsOuter.PkgTestsInner.APITests ~/work/Pkg.jl/Pkg.jl/test/api.jl:173
Pkg.precompile: Test Failed at /home/runner/work/Pkg.jl/Pkg.jl/test/api.jl:181
  Expression: !(occursin("Precompiling", String(take!(iob))))
   Evaluated: !(occursin("Precompiling", "    Updating registry at `/tmp/jl_GaJgXM/registries/General`\n    Updating git-repo `[https://github.com/JuliaRegistries/General.git`\n](https://github.com/JuliaRegistries/General.git%60/n)  No Changes to `/tmp/jl_hEt56v/Project.toml`\n  No Changes to `/tmp/jl_hEt56v/Manifest.toml`\nPrecompiling project...\n\e[91m  ✗ \e[39mBrokenDep\n  0 dependencies successfully precompiled in 1 seconds. 6 already precompiled.\n  \e[91m1\e[39m dependency errored. To see a full report either run `import Pkg; Pkg.precompile()` or load the package\n"))
Stacktrace:
 [1] macro expansion
   @ /opt/hostedtoolcache/julia/nightly/x64/share/julia/stdlib/v1.10/Test/src/Test.jl:477 [inlined]
 [2] (::Main.PkgTestsOuter.PkgTestsInner.APITests.var"#17#32")(tmp::String)
   @ Main.PkgTestsOuter.PkgTestsInner.APITests ~/work/Pkg.jl/Pkg.jl/test/api.jl:181
Pkg.precompile: Test Failed at /home/runner/work/Pkg.jl/Pkg.jl/test/api.jl:182
  Expression: length(Pkg.API.pkgs_precompile_suspended) == 1
   Evaluated: 0 == 1
Stacktrace:
 [1] macro expansion
   @ /opt/hostedtoolcache/julia/nightly/x64/share/julia/stdlib/v1.10/Test/src/Test.jl:477 [inlined]
 [2] (::Main.PkgTestsOuter.PkgTestsInner.APITests.var"#17#32")(tmp::String)
   @ Main.PkgTestsOuter.PkgTestsInner.APITests ~/work/Pkg.jl/Pkg.jl/test/api.jl:182

This PR

Pkg.precompile: Test Failed at /home/runner/work/Pkg.jl/Pkg.jl/test/api.jl:173
  Expression: length(broken_packages) == 1
   Evaluated: 0 == 1
Stacktrace:
 [1] macro expansion
   @ /opt/hostedtoolcache/julia/nightly/x64/share/julia/stdlib/v1.10/Test/src/Test.jl:477 [inlined]
 [2] (::Main.PkgTestsOuter.PkgTestsInner.APITests.var"#17#32")(tmp::String)
   @ Main.PkgTestsOuter.PkgTestsInner.APITests ~/work/Pkg.jl/Pkg.jl/test/api.jl:173

Pkg.precompile: Test Failed at /home/runner/work/Pkg.jl/Pkg.jl/test/api.jl:181
  Expression: !(occursin("Precompiling", String(take!(iob))))
   Evaluated: !(occursin("Precompiling", "    Updating registry at `/tmp/jl_GaJgXM/registries/General`\n    Updating git-repo `[https://github.com/JuliaRegistries/General.git`\n](https://github.com/JuliaRegistries/General.git%60/n)  No Changes to `/tmp/jl_hEt56v/Project.toml`\n  No Changes to `/tmp/jl_hEt56v/Manifest.toml`\nPrecompiling project...\n\e[91m  ✗ \e[39mBrokenDep\n  0 dependencies successfully precompiled in 1 seconds. 6 already precompiled.\n  \e[91m1\e[39m dependency errored. To see a full report either run `import Pkg; Pkg.precompile()` or load the package\n"))
Stacktrace:
 [1] macro expansion
   @ /opt/hostedtoolcache/julia/nightly/x64/share/julia/stdlib/v1.10/Test/src/Test.jl:477 [inlined]
 [2] (::Main.PkgTestsOuter.PkgTestsInner.APITests.var"#17#32")(tmp::String)
   @ Main.PkgTestsOuter.PkgTestsInner.APITests ~/work/Pkg.jl/Pkg.jl/test/api.jl:181

Pkg.precompile: Test Failed at /home/runner/work/Pkg.jl/Pkg.jl/test/api.jl:182
  Expression: length(Pkg.API.pkgs_precompile_suspended) == 1
   Evaluated: 0 == 1
Stacktrace:
 [1] macro expansion
   @ /opt/hostedtoolcache/julia/nightly/x64/share/julia/stdlib/v1.10/Test/src/Test.jl:477 [inlined]
 [2] (::Main.PkgTestsOuter.PkgTestsInner.APITests.var"#17#32")(tmp::String)
   @ Main.PkgTestsOuter.PkgTestsInner.APITests ~/work/Pkg.jl/Pkg.jl/test/api.jl:182