style: align error message wording in ndarray/ndarraylike2scalar

Use the standard "First argument must be an ndarray" wording shared by
sibling top-level ndarray wrappers (rot90, rot180, rotl90, to-rot90,
to-rotr90, flatten, unflatten).

Author: claude

lib/node_modules/@stdlib/ndarray/ndarraylike2scalar/lib/main.js

@@ -45,7 +45,7 @@ var format = require( '@stdlib/string/format' );
 */
 function ndarraylike2scalar( x ) {
 	if ( !isndarrayLike( x ) ) {
-		throw new TypeError( format( 'invalid argument. Must provide an ndarray. Value: `%s`.', x ) );
+		throw new TypeError( format( 'invalid argument. First argument must be an ndarray. Value: `%s`.', x ) );
 	}
 	return base( x );
 }