internal/regtest: skip TestProgressBarErrors: it is too flaky

Updates golang/go#46930

Change-Id: I7bfaccf6b632623218450532e82cbd0ff45f49b7
Reviewed-on: https://go-review.googlesource.com/c/tools/+/361156
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>

gopls/internal/regtest/diagnostics/diagnostics_test.go

@@ -1509,6 +1509,7 @@ package foo_
 // TestProgressBarErrors confirms that critical workspace load errors are shown
 // and updated via progress reports.
 func TestProgressBarErrors(t *testing.T) {
+	t.Skip("too flaky: golang/go#46930")
 	testenv.NeedsGo1Point(t, 14)
 
 	const pkg = `