js: Remove external source map option

It was merged by accident and the implementation does not look correct.

Fixes #7932

resources/resource_transformers/js/options_test.go

@@ -93,7 +93,7 @@ func TestToBuildOptions(t *testing.T) {
 
 	opts, err = toBuildOptions(Options{
 		Target: "es2018", Format: "cjs", Minify: true, mediaType: media.JavascriptType,
-		SourceMap: "external"})
+		SourceMap: "inline"})
 	c.Assert(err, qt.IsNil)
 	c.Assert(opts, qt.DeepEquals, api.BuildOptions{
 		Bundle:            true,
@@ -102,7 +102,7 @@ func TestToBuildOptions(t *testing.T) {
 		MinifyIdentifiers: true,
 		MinifySyntax:      true,
 		MinifyWhitespace:  true,
-		Sourcemap:         api.SourceMapExternal,
+		Sourcemap:         api.SourceMapInline,
 		Stdin: &api.StdinOptions{
 			Loader: api.LoaderJS,
 		},