Update src/WP_CLI/CommandWithUpgrade.php

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: swissspidy

src/WP_CLI/CommandWithUpgrade.php

@@ -1197,7 +1197,7 @@ protected function get_raw_url_from_gist( $gist_id ) {
 		$api_url = 'https://api.github.com/gists/' . $gist_id;
 		$token   = getenv( 'GITHUB_TOKEN' );
 
-		$request_arguments = $token ? [ 'headers' => 'Authorization: Bearer ' . $token ] : [];
+		$request_arguments = $token ? [ 'headers' => [ 'Authorization' => 'Bearer ' . $token ] ] : [];
 
 		$response = \wp_remote_get( $api_url, $request_arguments );