Upgrade/Install: Silence Requests deprecations before preloading.

Intentional preloading of Requests 2.x classes and interfaces using their old (Requests 1.x) names should not produce deprecation notices.

This commit defines `REQUESTS_SILENCE_PSR0_DEPRECATIONS` as `true` in `_preload_old_requests_classes_and_interfaces()`.

Follow-up to [54997], [55007], [55046].

Props costdev, afragen, jrf.
Fixes #54504.

git-svn-id: https://develop.svn.wordpress.org/trunk@55225 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/update-core.php

@@ -1599,6 +1599,10 @@ function update_core( $from, $to ) {
 function _preload_old_requests_classes_and_interfaces( $to ) {
 	global $_old_requests_files, $wp_filesystem;
 
+	if ( ! defined( 'REQUESTS_SILENCE_PSR0_DEPRECATIONS' ) ) {
+		define( 'REQUESTS_SILENCE_PSR0_DEPRECATIONS', true );
+	}
+
 	foreach ( $_old_requests_files as $name => $file ) {
 		// Skip files that aren't interfaces or classes.
 		if ( is_int( $name ) ) {