Improve JSDoc wording

src/vs/editor/common/editorCommon.ts

@@ -243,10 +243,9 @@ export interface IEditorOptions {
 	 */
 	roundedSelection?: boolean;
 	/**
-	 * Theme to be used for rendering. Consists of two parts, the UI theme and the syntax theme,
-	 * separated by a space.
-	 * The current available UI themes are: 'vs' (default), 'vs-dark', 'hc-black'
-	 * The syntax themes are contributed. The default is 'default-theme'
+	 * Theme to be used for rendering.
+	 * The current out-of-the-box available themes are: 'vs' (default), 'vs-dark', 'hc-black'.
+	 * You can create custom themes via `monaco.editor.defineTheme`.
 	 */
 	theme?: string;
 	/**

src/vs/monaco.d.ts

@@ -1154,10 +1154,9 @@ declare module monaco.editor {
          */
         roundedSelection?: boolean;
         /**
-         * Theme to be used for rendering. Consists of two parts, the UI theme and the syntax theme,
-         * separated by a space.
-         * The current available UI themes are: 'vs' (default), 'vs-dark', 'hc-black'
-         * The syntax themes are contributed. The default is 'default-theme'
+         * Theme to be used for rendering.
+         * The current out-of-the-box available themes are: 'vs' (default), 'vs-dark', 'hc-black'.
+         * You can create custom themes via `monaco.editor.defineTheme`.
          */
         theme?: string;
         /**