portico: Remove `bootstrap-btn.css` dependency from portico.

This commit removes the final vestiges of `bootstrap-btn.css` from
portico, allowing us to move `bootstrap-btn.css` from `common.ts` bundle
to just `app.ts` bundle.

templates/zerver/development/integrations_dev_panel.html

@@ -95,8 +95,8 @@
             </div>
             <textarea id="fixture_body"></textarea>
             <div class="buttons">
-                <button id="send_all_fixtures_button" class="bootstrap-btn">Send all</button>
-                <button id="send_fixture_button" class="bootstrap-btn">Send!</button>
+                <button id="send_all_fixtures_button">Send all</button>
+                <button id="send_fixture_button">Send!</button>
             </div>
         </div>
         <div class="col1">

web/src/bundles/app.ts

@@ -23,6 +23,7 @@ import "katex/dist/katex.css";
 import "flatpickr/dist/flatpickr.css";
 import "flatpickr/dist/plugins/confirmDate/confirmDate.css";
 import "../../third/bootstrap/css/bootstrap.app.css";
+import "../../third/bootstrap/css/bootstrap-btn.css";
 import "../../styles/typeahead.css";
 import "../../styles/app_variables.css";
 import "../../styles/tooltips.css";

web/src/bundles/common.ts

@@ -3,7 +3,6 @@ import "../../debug-require.cjs";
 import "../alert_popup.ts";
 import "../csrf.ts";
 import "../blueslip.ts";
-import "../../third/bootstrap/css/bootstrap-btn.css";
 import "simplebar/dist/simplebar.css";
 import "font-awesome/css/font-awesome.css";
 import "../../images/icons/zulip-icons.font.cjs";

web/styles/portico/integrations_dev_panel.css

@@ -116,9 +116,10 @@
     margin-right: 2%;
 
     button {
+        padding: 6px 12px;
         color: hsl(0deg 0% 100%);
         background-color: hsl(208deg 56% 53%);
-        border-color: hsl(208deg 56% 47%);
+        border: 1px solid hsl(208deg 56% 47%);
 
         &:hover,
         &:active,