os/exec: adjust function name in fatal message

CL 481620 changed the test to use LookPath.

Change-Id: Ie7b3110775b586701b6df6aeee38f26402227eb4
Reviewed-on: https://go-review.googlesource.com/c/go/+/529095
Reviewed-by: Bryan Mills <[email protected]>
Auto-Submit: Bryan Mills <[email protected]>
TryBot-Bypass: Bryan Mills <[email protected]>
Auto-Submit: Tobias Klauser <[email protected]>
Run-TryBot: Bryan Mills <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>

Author: tklauser

src/os/exec/lp_linux_test.go

@@ -50,7 +50,7 @@ func TestFindExecutableVsNoexec(t *testing.T) {
 	// Check that it works as expected.
 	_, err = exec.LookPath(path)
 	if err != nil {
-		t.Fatalf("findExecutable: got %v, want nil", err)
+		t.Fatalf("LookPath: got %v, want nil", err)
 	}
 
 	for {