Hide VS Code action buttons placed in sidebar panel headers

In GH-179 the Custom CSS and JS Loader (1) extension was introduced to
use custom CSS stylesheets including styles to hide VS Code's menu
buttons from the editor.
To hide the button of sidebar panels headers another selector has been
added.

References:
  (1) https://marketplace.visualstudio.com/items?itemName=be5invis.vscode-custom-css

Resolves GH-200

snowblocks/visual-studio-code/css/remove-action-button.css

@@ -27,3 +27,6 @@
 .panel-header.expanded .actions {
   display: none !important;
 }
+.sidebar .title-actions .actions-container {
+  display: none !important;
+}