refactor(@angular/build): template style elements should always be CSS

Now that style elements within templates are processed as inline component
styles, the style contents should only be considered CSS. This ensures
consistent behavior prior to when style elements were processed. It also ensures
that the styles will function as expected in JIT mode where template styles
cannot be preprocessed and must be written in a browser supported language.

packages/angular/build/src/tools/esbuild/angular/compiler-plugin.ts

@@ -185,7 +185,8 @@ export function createCompilerPlugin(
               stylesheetResult = await stylesheetBundler.bundleInline(
                 data,
                 containingFile,
-                styleOptions.inlineStyleLanguage,
+                // Inline stylesheets from a template style element are always CSS
+                containingFile.endsWith('.html') ? 'css' : styleOptions.inlineStyleLanguage,
               );
             }