[bugfix] #1874 Add Bootstrap form style for CodeMirror editor

Fix a bug in the Search/Replace form of the CodeMirror editor, caused by an unwanted style which Bootstrap applied.

The bug makes it difficult to select some elements of the Search/Replace dialog.

Related issue: https://github.com/gchq/CyberChef/issues/1874

src/web/stylesheets/utils/_overrides.css

@@ -249,6 +249,13 @@ optgroup {
 }
 
 
+/* Bootstrap form inside CodeMirror editor */
+
+.cm-panel > .bmd-form-group {
+  padding-top: 0;
+}
+
+
 /* CodeMirror */
 
 .ͼ2 .cm-specialChar,