Breaking Change: Remove deprecated PHP APIs

-Google\Protobuf\Field_Kind: use Google\Protobuf\Field\Kind instead
-Google/Protobuf\Field_Cardinality: use Google\Protobuf\Field\Cardinality instead
-Google\Protobuf\Internal\RepeatedField: use Google\Protobuf\RepeatedField instead

https://protobuf.dev/news/2025-09-19/#php-remove-apis

PiperOrigin-RevId: 843471652

Author: anandolee

php/BUILD.bazel

@@ -19,8 +19,6 @@ _RUNTIME_SOURCES = [
     "src/Google/Protobuf/DescriptorPool.php",
     "src/Google/Protobuf/EnumDescriptor.php",
     "src/Google/Protobuf/EnumValueDescriptor.php",
-    "src/Google/Protobuf/Field_Cardinality.php",
-    "src/Google/Protobuf/Field_Kind.php",
     "src/Google/Protobuf/FieldDescriptor.php",
     "src/Google/Protobuf/Internal/AnyBase.php",
     "src/Google/Protobuf/Internal/CodedInputStream.php",
@@ -48,7 +46,6 @@ _RUNTIME_SOURCES = [
     "src/Google/Protobuf/Internal/OneofDescriptor.php",
     "src/Google/Protobuf/Internal/OneofField.php",
     "src/Google/Protobuf/Internal/RawInputStream.php",
-    "src/Google/Protobuf/Internal/RepeatedField.php",
     "src/Google/Protobuf/Internal/RepeatedFieldIter.php",
     "src/Google/Protobuf/Internal/TimestampBase.php",
     "src/Google/Protobuf/OneofDescriptor.php",