Remove submodule re-added by accident

This was removed in bytecodealliance#6195 but re-added in bytecodealliance#6877, I believe by accident,
so this re-deletes it. I've also edited `.gitmodules` a bit while I was
here to remove it and additionally keep other entries up-to-date with
matching paths.

.gitmodules

@@ -1,10 +1,10 @@
-[submodule "spec_testsuite"]
+[submodule "tests/spec_testsuite"]
  path = tests/spec_testsuite
  url = https://github.com/WebAssembly/testsuite
-[submodule "crates/c-api/examples/wasm-c-api"]
+[submodule "crates/c-api/wasm-c-api"]
  path = crates/c-api/wasm-c-api
  url = https://github.com/WebAssembly/wasm-c-api
-[submodule "WASI"]
+[submodule "crates/wasi-common/WASI"]
  path = crates/wasi-common/WASI
  url = https://github.com/WebAssembly/WASI
 [submodule "crates/wasi-nn/spec"]
@@ -13,10 +13,7 @@
 [submodule "tests/wasi_testsuite/wasi-threads"]
  path = tests/wasi_testsuite/wasi-threads
  url = https://github.com/WebAssembly/wasi-threads
-[submodule "crates/wasi-http/wasi-http"]
- path = crates/wasi-http/wasi-http
- url = https://github.com/WebAssembly/wasi-http
-[submodule "tests/wasi_testsuite/wasi"]
+[submodule "tests/wasi_testsuite/wasi-common"]
  path = tests/wasi_testsuite/wasi-common
  url = https://github.com/WebAssembly/wasi-testsuite.git
  branch = prod/testsuite-base