debug/pe: use ws2_32.dll in TestImportTableInUnknownSection

Apparently (see
https://github.com/golang/go/issues/27904#issuecomment-442140627
for details) kernel32.dll file is not present on windows/arm, so
use ws2_32.dll instead. ws2_32.dll imports table also lives in
'.rdata' section, so ws2_32.dll is as good as kernel32.dll for
testing issue #16103.

Updates #27904

Change-Id: Ibc72b24eea9a4d85abd371ffdcf00442e711b745
Reviewed-on: https://go-review.googlesource.com/c/151480Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

src/debug/pe/file_test.go

@@ -603,9 +603,9 @@ func TestImportTableInUnknownSection(t *testing.T) {
 		t.Skip("skipping Windows-only test")
 	}
 
-	// kernel32.dll import table is located in ".rdata" section,
+	// ws2_32.dll import table is located in ".rdata" section,
 	// so it is good enough to test issue #16103.
-	const filename = "kernel32.dll"
+	const filename = "ws2_32.dll"
 	path, err := exec.LookPath(filename)
 	if err != nil {
 		t.Fatalf("unable to locate required file %q in search path: %s", filename, err)