cmd/go: remove unused (*testgoData).mustHaveContent test helper

It's unused since CL 214382.

Change-Id: I83a860938f87a7c4d2bdb966689c17ba29066639
Reviewed-on: https://go-review.googlesource.com/c/go/+/537596
Reviewed-by: Bryan Mills <[email protected]>
Reviewed-by: David Chase <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: tklauser

src/cmd/go/go_test.go

@@ -791,19 +791,6 @@ func (tg *testgoData) mustNotExist(path string) {
 	}
 }
 
-// mustHaveContent succeeds if filePath is a path to a file,
-// and that file is readable and not empty.
-func (tg *testgoData) mustHaveContent(filePath string) {
-	tg.mustExist(filePath)
-	f, err := os.Stat(filePath)
-	if err != nil {
-		tg.t.Fatal(err)
-	}
-	if f.Size() == 0 {
-		tg.t.Fatalf("expected %s to have data, but is empty", filePath)
-	}
-}
-
 // wantExecutable fails with msg if path is not executable.
 func (tg *testgoData) wantExecutable(path, msg string) {
 	tg.t.Helper()