[clang-format] Remove requirement that port_platform.h is at the top (#36275)

Closes #36275

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/36275 from ctiller:port_platform-include-grpcpp-impl-clang-format 89c43491d0
PiperOrigin-RevId: 623178498

include/grpcpp/impl/.clang-format

@@ -5,9 +5,6 @@ DerivePointerAlignment: false
 PointerAlignment: Left
 IncludeBlocks: Regroup
 IncludeCategories:
-  # port_platform.h is before almost everything
-  - Regex: '^<grpc/(support|impl/codegen)/port_platform.h>'
-    Priority: -100
   # ruby.h is even more first if it's included
   - Regex: '^<ruby/ruby.h>'
     Priority: -200

include/grpcpp/impl/status.h

@@ -21,9 +21,8 @@
 
 // IWYU pragma: private, include <grpcpp/support/status.h>
 
-#include <grpc/support/port_platform.h>
-
 #include <grpc/status.h>
+#include <grpc/support/port_platform.h>
 #include <grpcpp/support/config.h>
 #include <grpcpp/support/status_code_enum.h>