internal/frontend: remove ** from glob pattern

Go's glob patterns do not treat "**" as meaning "all directories
below, recursively." Instead, "**" means the same as "*". So

  shared/**/*.tmpl

is legal but retrieves only files that are one level down
from "shared".

Currently this isn't a problem, but it would be if a subdirectory of
"shared" had its own subdirectory with *.tmpl files.

Remove the "**" to make this clear.

Change-Id: Ia57212eb55347705af49e2e42cbe9948e14370be
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/359034
Trust: Jonathan Amsterdam <jba@google.com>
Run-TryBot: Jonathan Amsterdam <jba@google.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Julie Qiu <julie@golang.org>
Reviewed-by: Jamal Carvalho <jamal@golang.org>
diff --git a/internal/frontend/server.go b/internal/frontend/server.go
index f7b3f48..e51f901 100644
--- a/internal/frontend/server.go
+++ b/internal/frontend/server.go
@@ -620,7 +620,7 @@
 		if err != nil {
 			return nil, fmt.Errorf("ParseFilesFromTrustedSources: %v", err)
 		}
-		helperGlob := join(base, tsc("shared/**/*.tmpl"))
+		helperGlob := join(base, tsc("shared/*/*.tmpl"))
 		if _, err := t.ParseGlobFromTrustedSource(helperGlob); err != nil {
 			return nil, fmt.Errorf("ParseGlobFromTrustedSource(%q): %v", helperGlob, err)
 		}