gopls/internal/test/integration: fix flakiness of TestResolveImportCycle

Avoid flaky dependence on go list error messages in
TestResolveImportCycle. It would be better if we could guarantee that
the error is from go list, but since the error from golang/go#64899 is
reasonable, it is best to just avoid the flake for now.

Fixes golang/go#64899

Change-Id: If5038acbdf020323d8fa9db0d8e1e8e054cfe464
Reviewed-on: https://go-review.googlesource.com/c/tools/+/556495
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>

gopls/internal/test/integration/diagnostics/diagnostics_test.go

@@ -1672,12 +1672,17 @@ const B = a.B
 		env.OpenFile("b/b.go")
 		env.AfterChange(
 			// The Go command sometimes tells us about only one of the import cycle
-			// errors below. For robustness of this test, succeed if we get either.
+			// errors below. Also, sometimes we get an error during type checking
+			// instead of during list, due to missing metadata. This is likely due to
+			// a race.
+			// For robustness of this test, succeed if we get any reasonable error.
 			//
 			// TODO(golang/go#52904): we should get *both* of these errors.
+			// TODO(golang/go#64899): we should always get an import cycle error
+			// rather than a missing metadata error.
 			AnyOf(
-				Diagnostics(env.AtRegexp("a/a.go", `"mod.test/b"`), WithMessage("import cycle")),
-				Diagnostics(env.AtRegexp("b/b.go", `"mod.test/a"`), WithMessage("import cycle")),
+				Diagnostics(env.AtRegexp("a/a.go", `"mod.test/b"`)),
+				Diagnostics(env.AtRegexp("b/b.go", `"mod.test/a"`)),
 			),
 		)
 		env.RegexpReplace("b/b.go", `const B = a\.B`, "")