Taxonomy: Fix deprecated calls to get_terms().

The taxonomy should be passed as part of `$args`, rather than as its own argument.

Props sgastard, mukesh27, SergeyBiryukov.
Fixes #47819.

git-svn-id: https://develop.svn.wordpress.org/trunk@45723 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/export.php

@@ -159,7 +159,12 @@ function export_wp( $args = array() ) {
 		$tags       = (array) get_tags( array( 'get' => 'all' ) );
 
 		$custom_taxonomies = get_taxonomies( array( '_builtin' => false ) );
-		$custom_terms      = (array) get_terms( $custom_taxonomies, array( 'get' => 'all' ) );
+		$custom_terms      = (array) get_terms(
+			array(
+				'taxonomy' => $custom_taxonomies,
+				'get'      => 'all',
+			)
+		);
 
 		// Put categories in order with no child going before its parent.
 		while ( $cat = array_shift( $categories ) ) {