Fix: Update homepage URL in composer.json (#635)

Avoid redirection:
- From: https://github.com/firebase/php-jwt
- To: https://github.com/googleapis/php-jwt

Co-authored-by: Brent Shaffer <betterbrent@google.com>

Author: glensc

composer.json

@@ -1,7 +1,7 @@
 {
     "name": "firebase/php-jwt",
     "description": "A simple library to encode and decode JSON Web Tokens (JWT) in PHP. Should conform to the current spec.",
-    "homepage": "https://github.com/firebase/php-jwt",
+    "homepage": "https://github.com/googleapis/php-jwt",
     "keywords": [
         "php",
         "jwt"