bootstrap: Remove last vestiges of bootstrap-tooltip library.

Everything but this sliver of CSS has been deleted previously as part
of our migration off Bootstrap.

docs/THIRDPARTY

@@ -146,11 +146,6 @@ Files: web/third/bootstrap/js/bootstrap.js
 Copyright: 2012 Twitter, Inc.
 License: Apache-2.0
 
-Files: web/third/bootstrap-tooltip/*
-Copyright: 2012 Twitter, Inc.
-License: Apache-2.0
-Comment: Bootstrap tooltip and bootstrap popover.  The software has been modified.
-
 Files: web/third/bootstrap-typeahead/*
 Copyright: 2012 Twitter, Inc.
 License: Apache-2.0

web/src/bundles/app.ts

@@ -21,7 +21,6 @@ import "../zulip_test";
 // Import styles
 import "tippy.js/dist/tippy.css";
 import "tippy.js/themes/light-border.css";
-import "../../third/bootstrap-tooltip/tooltip.css";
 import "spectrum-colorpicker/spectrum.css";
 import "katex/dist/katex.css";
 import "flatpickr/dist/flatpickr.css";

web/third/bootstrap-tooltip/tooltip.css

@@ -1,43 +0,0 @@
-/* TODO: Audit and purge use of these styles from our popovers and delete this. */
-
-.popover {
-  position: absolute;
-  top: 0;
-  left: 0;
-  z-index: 1010;
-  display: none;
-  width: 236px;
-  padding: 1px;
-  background-color: #ffffff;
-  border: 1px solid #ccc;
-  border: 1px solid rgba(0, 0, 0, 0.2);
-  -webkit-border-radius: 6px;
-     -moz-border-radius: 6px;
-          border-radius: 6px;
-  -webkit-box-shadow: 0 5px 10px rgba(0, 0, 0, 0.2);
-     -moz-box-shadow: 0 5px 10px rgba(0, 0, 0, 0.2);
-          box-shadow: 0 5px 10px rgba(0, 0, 0, 0.2);
-  -webkit-background-clip: padding-box;
-     -moz-background-clip: padding;
-          background-clip: padding-box;
-}
-.popover-title {
-  padding: 8px 14px;
-  margin: 0;
-  font-size: 14px;
-  font-weight: normal;
-  line-height: 18px;
-  background-color: #f7f7f7;
-  border-bottom: 1px solid #ebebeb;
-  -webkit-border-radius: 5px 5px 0 0;
-     -moz-border-radius: 5px 5px 0 0;
-          border-radius: 5px 5px 0 0;
-}
-.popover-content {
-  padding: 9px 14px;
-}
-.popover-content p,
-.popover-content ul,
-.popover-content ol {
-  margin-bottom: 0;
-}