FolderPicker: Prevent dropdown menu from disappearing off screen (#32603)

* fix(folderpicker): remove position fixed so menu works in panel editor for dashlist & alertlist

* test(folderpicker): update snapshot

public/app/core/components/Select/FolderPicker.tsx

@@ -161,7 +161,6 @@ export class FolderPicker extends PureComponent<Props, State> {
           loadOptions={this.debouncedSearch}
           onChange={this.onFolderChange}
           onCreateOption={this.createNewFolder}
-          menuPosition="fixed"
         />
       </div>
     );

public/app/core/components/Select/__snapshots__/FolderPicker.test.tsx.snap

@@ -10,7 +10,6 @@ exports[`FolderPicker should render 1`] = `
     defaultValue={Object {}}
     loadOptions={[Function]}
     loadingMessage="Loading folders..."
-    menuPosition="fixed"
     onChange={[Function]}
     onCreateOption={[Function]}
     value={Object {}}