Always dispose of DecorationCSSRules

Found while looking into #63467

There's potential leak for `DecorationCSSRules`. Currently we only dipose of them if `hasContent` is true, which I'm not sure guarantees that these classes are truely non-disposable

With this change, we always dispose of them. At worst, these extra dispose call should be noops

src/vs/editor/browser/services/codeEditorServiceImpl.ts

@@ -141,18 +141,18 @@ class DecorationTypeOptionsProvider implements IModelDecorationOptionsProvider {
 		this.refCount = 0;
 		this._disposables = [];
 
-		let createCSSRules = (type: ModelDecorationCSSRuleType) => {
-			let rules = new DecorationCSSRules(type, providerArgs, themeService);
-			if (rules.hasContent) {
+		const createCSSRules = (type: ModelDecorationCSSRuleType) => {
+			const rules = new DecorationCSSRules(type, providerArgs, themeService);
 			this._disposables.push(rules);
+			if (rules.hasContent) {
 				return rules.className;
 			}
 			return void 0;
 		};
-		let createInlineCSSRules = (type: ModelDecorationCSSRuleType) => {
-			let rules = new DecorationCSSRules(type, providerArgs, themeService);
-			if (rules.hasContent) {
+		const createInlineCSSRules = (type: ModelDecorationCSSRuleType) => {
+			const rules = new DecorationCSSRules(type, providerArgs, themeService);
 			this._disposables.push(rules);
+			if (rules.hasContent) {
 				return { className: rules.className, hasLetterSpacing: rules.hasLetterSpacing };
 			}
 			return null;