fix: centering/aligning of file-button by removing flex-grow (marimo-team#5266)

Fixes marimo-team#5265

Author: mscolnick

frontend/src/plugins/impl/FileUploadPlugin.tsx

@@ -184,7 +184,7 @@ export const FileUpload = (props: FileUploadProps): JSX.Element => {
     const label = props.label ?? "Upload";
     return (
       <TooltipProvider>
-        <div className="flex flex-row items-center justify-start flex-grow gap-2">
+        <div className="flex flex-row items-center justify-start gap-2">
           <button
             data-testid="marimo-plugin-file-upload-button"
             {...getRootProps({})}