Update glyph margin CSS rule names (microsoft#185594)

Author: joyceerhl

src/vs/editor/browser/viewParts/glyphMargin/glyphMargin.css

@@ -12,7 +12,7 @@
 	Keeping name short for faster parsing.
 	cgmr = core glyph margin rendering (div)
 */
-.monaco-editor .margin-view-overlays .cgmr {
+.monaco-editor .glyph-margin-widgets .cgmr {
 	position: absolute;
 	display: flex;
 	align-items: center;

src/vs/editor/browser/viewParts/glyphMargin/glyphMargin.ts

@@ -139,7 +139,7 @@ export class GlyphMarginWidgets extends ViewPart {
 		const layoutInfo = options.get(EditorOption.layoutInfo);
 
 		this.domNode = createFastDomNode(document.createElement('div'));
-		this.domNode.setClassName('glyphMarginWidgets');
+		this.domNode.setClassName('glyph-margin-widgets');
 		this.domNode.setPosition('absolute');
 		this.domNode.setTop(0);