cmd/guru: fix tests for line directives in Go 1.11

Go 1.11 changed the behavior of line directives, so reflect that in the
golden files for tests.

Change-Id: I7df282dfbeb3bfc5d75481c345acf724bb0b25bf
Reviewed-on: https://go-review.googlesource.com/128999
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>

cmd/guru/guru_test.go

@@ -268,11 +268,6 @@ func TestGuru(t *testing.T) {
 				// tests once we drop support for go1.8.
 				t.Skip()
 			}
-			if filename == "testdata/src/referrers/main.go" && !contains(build.Default.ReleaseTags, "go1.11") {
-				// Disabling broken test on Go 1.9 and Go 1.10. https://golang.org/issue/24421
-				// TODO(gri,adonovan): fix this test.
-				t.Skip()
-			}
 
 			json := strings.Contains(filename, "-json/")
 			queries := parseQueries(t, filename)

cmd/guru/testdata/src/referrers/main.golden

@@ -60,5 +60,5 @@ references to var notexported int
 
 -------- @referrers ref-type-U --------
 references to type U int
-open nosuchfile.y: no such file or directory (+ 1 more refs in this file)
+open testdata/src/referrers/nosuchfile.y: no such file or directory (+ 1 more refs in this file)