fix(amazonq): Update dropdown behavior to native dropdowns

Author: manodnyab

plugins/amazonq/chat/jetbrains-community/src/software/aws/toolkits/jetbrains/services/amazonq/webview/Browser.kt

@@ -221,6 +221,14 @@ class Browser(parent: Disposable, private val webUri: URI, val project: Project)
                         box-shadow: none !important;
                         border-radius: 0 !important;
                     }
+                    select.mynah-form-input {
+                        -webkit-appearance: menulist !important;
+                        appearance: menulist !important;
+                        padding: 0px var(--mynah-sizing-2);
+                    }
+                    .mynah-select-handle {
+                        visibility: hidden;
+                    }
                     .mynah-ui-spinner-container > span.mynah-ui-spinner-logo-part > .mynah-ui-spinner-logo-mask.text {
                         will-change: transform !important;
                         transform: translateZ(0) !important;