chore: drop protobuf 3 runtime (#8519)

Author: bshaffer

CloudCommonProtos/composer.json

@@ -8,7 +8,7 @@
   "homepage": "https://github.com/googleapis/google-cloud-php-common-protos",
   "license": "Apache-2.0",
   "require": {
-    "google/protobuf": "^v3.25.3||^4.26.1",
+    "google/protobuf": "^4.26.1",
     "google/common-protos": "^3.0||^4.0"
   },
   "require-dev": {

CommonProtos/composer.json

@@ -10,7 +10,7 @@
   "license": "Apache-2.0",
   "require": {
     "php": "^8.1",
-    "google/protobuf": "^v3.25.3||^4.26.1"
+    "google/protobuf": "^4.26.1"
   },
   "require-dev": {
     "phpunit/phpunit": "^9.6"

ShoppingCommonProtos/composer.json

@@ -18,7 +18,7 @@
     },
     "require": {
         "php": "^8.1",
-        "google/protobuf": "^v3.25.3||^4.26.1"
+        "google/protobuf": "^4.26.1"
     },
     "require-dev": {
         "phpunit/phpunit": "^9.0"