Remove unused `tooltip` SASS module

src/styles/sidebar/components/tooltip.scss

-@use "../../variables" as var;
-
-// Tooltips
-// --------
-// Custom tooltips that appear instantly, replacing the browser's default
-// tooltip
-
-@mixin tooltip-arrow($rotation) {
-  transform: rotate($rotation);
-  background: var.$grey-7;
-  border-bottom: 1px solid rgba(0, 0, 0, 0.2);
-  border-right: 1px solid rgba(0, 0, 0, 0.2);
-  content: '';
-  display: block;
-  height: 6px;
-  left: 0;
-  margin-left: auto;
-  margin-right: 5px;
-  position: absolute;
-  right: 0;
-  width: 6px;
-}
-
-// The tooltip background
-.tooltip {
-  @include var.font-small;
-
-  border-radius: 2px;
-  position: fixed;
-  background-color: var.$grey-7;
-  color: white;
-  font-weight: bold;
-  padding-left: 5px;
-  padding-right: 5px;
-  padding-top: 4px;
-  padding-bottom: 4px;
-  z-index: var.$zindex-tooltip;
-}
-
-// Arrow at the bottom of the tooltip pointing at the target element
-
-// Variant for tooltips above the target that point down at it
-.tooltip--down:before {
-  @include tooltip-arrow(45deg);
-  content: '';
-  top: calc(100% - 5px);
-}
-
-// Variant for tooltips below the target that point up at it
-.tooltip--up:before {
-  @include tooltip-arrow(225deg);
-  content: '';
-  top: -3px;
-}
-
-// The text content inside the tooltip
-.tooltip-label {
-  // Make the label a positioned element so that it appears _above_ the
-  // tooltip's arrow, which partially overlaps the content of the tooltip.
-  position: relative;
-}

src/styles/sidebar/sidebar.scss

@@ -54,7 +54,6 @@
 @use './components/thread-card';
 @use './components/thread-list';
 @use './components/toast-messages';
-@use './components/tooltip';
 @use './components/top-bar';
 @use './components/tutorial';
 @use './components/version-info';