Update high contrast styles for buttons and inputs (#3343)

Author: daviddossett

webviews/common/common.css

@@ -122,7 +122,7 @@ body img.avatar {
 }
 
 .avatar-link {
-	flex-shrink: 0;;
+	flex-shrink: 0;
 }
 
 .section-item .avatar-link {
@@ -164,10 +164,15 @@ body img.avatar {
 
 /** Theming */
 
-.vscode-high-contrast button,
+.vscode-high-contrast button {
+	outline: none;
+	background: var(--vscode-button-background);
+	border: 1px solid var(--vscode-contrastBorder);
+}
+
 .vscode-high-contrast input {
 	outline: none;
-	background: none !important;
+	background: var(--vscode-input-background);
 	border: 1px solid var(--vscode-contrastBorder);
 }