fix microsoft#195344 (microsoft#196563)

Author: sandy081

src/vs/workbench/browser/parts/panel/media/panelpart.css

@@ -41,6 +41,12 @@
 	background-color: var(--vscode-panel-background);
 }
 
+.monaco-workbench .part.panel > .content .suggest-input-container .monaco-editor,
+.monaco-workbench .part.panel > .content .suggest-input-container .monaco-editor .margin,
+.monaco-workbench .part.panel > .content .suggest-input-container .monaco-editor .monaco-editor-background {
+	background-color: inherit;
+}
+
 .monaco-workbench .part.panel > .title > .composite-bar-container >.composite-bar > .monaco-action-bar .action-item:focus .action-label,
 .monaco-workbench .part.panel > .title > .composite-bar-container >.composite-bar > .monaco-action-bar .action-item:hover .action-label {
 	color: var(--vscode-panelTitle-activeForeground) !important;