fix(CDropdown): correct default variant value from 'btn-group' to 'dropdown'

The default variant prop was incorrectly set to 'btn-group' instead of the correct 'dropdown' value. This fix ensures the component uses the proper default styling and behavior.

Author: mrholek

packages/coreui-react/src/components/dropdown/CDropdown.tsx

@@ -226,7 +226,7 @@ export const CDropdown: PolymorphicRefForwardingComponent<'div', CDropdownProps>
       popperConfig,
       portal = false,
       reference = 'toggle',
-      variant = 'btn-group',
+      variant = 'dropdown',
       visible = false,
       ...rest
     },

packages/docs/content/api/CDropdown.api.mdx

@@ -216,7 +216,7 @@ const myContainer = document.getElementById('my-container')
       </tr>
       <tr id="cdropdown-variant">
         <td className="text-primary fw-semibold">variant<a href="#cdropdown-variant" aria-label="CDropdown variant permalink" className="anchor-link after">#</a></td>
-        <td><code>{`btn-group`}</code></td>
+        <td><code>{`dropdown`}</code></td>
         <td><code>{`'btn-group'`}</code>, <code>{`'dropdown'`}</code>, <code>{`'input-group'`}</code>, <code>{`'nav-item'`}</code></td>
       </tr>
       <tr>

packages/docs/src/components/Sidebar.tsx

@@ -52,7 +52,7 @@ const Sidebar: FC = () => {
           </CSidebarBrand>
           <div className="text-body-secondary mx-3 mb-2 small fw-semibold">Framework:</div>
           <CDropdown className="mx-3 mb-4">
-            <CDropdownToggle color="primary" variant="outline">
+            <CDropdownToggle className="w-100" color="primary" variant="outline">
               React.js
             </CDropdownToggle>
             <CDropdownMenu className="w-100">