debug/pe: correct TestImportTableInUnknownSection error message

TestImportTableInUnknownSection uses kernel32.dll file, but the error
message mentions atmfd.dll. Adjust error message to match the test.

This change should have been part of CL 151137.

Updates #27904

Change-Id: Ifc31a12134b328472191122f8426ab6ed234fbd4
Reviewed-on: https://go-review.googlesource.com/c/151477
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>

src/debug/pe/file_test.go

@@ -605,9 +605,10 @@ func TestImportTableInUnknownSection(t *testing.T) {
 
 	// kernel32.dll import table is located in ".rdata" section,
 	// so it is good enough to test issue #16103.
-	path, err := exec.LookPath("kernel32.dll")
+	const filename = "kernel32.dll"
+	path, err := exec.LookPath(filename)
 	if err != nil {
-		t.Fatalf("unable to locate required file %q in search path: %s", "atmfd.dll", err)
+		t.Fatalf("unable to locate required file %q in search path: %s", filename, err)
 	}
 
 	f, err := Open(path)