Fix icon sizing for themes with custom font-sizes

Fixes microsoft#13719

Author: mjbvz

src/vs/workbench/contrib/chat/browser/media/chat.css

@@ -1249,12 +1249,14 @@ have to be updated for changes to the rules above, or to support more deeply nes
 }
 
 .interactive-session .chat-attached-context .chat-attached-context-attachment .monaco-icon-label::before {
-	height: 90%;
+	height: 1em;
 	width: auto;
 	padding: 0;
 	line-height: 1em !important;
 	align-self: center;
 
+	font-size: 100%;
+
 	background-size: contain;
 	background-position: center;
 	background-repeat: no-repeat;

src/vs/workbench/contrib/chat/browser/media/chatInlineAnchorWidget.css

@@ -39,6 +39,7 @@
 	display: inline-block;
 	line-height: 100%;
 	overflow: hidden;
+	font-size: 100% !important;
 
 	background-size: contain;
 	background-position: center;