Merge pull request #20433 from tanjunchen/clean-doc

include/grpc/impl/codegen/port_platform.h

...hannel/resolver/dns/c_ares/grpc_ares_ev_driver_windows.cc

src/core/tsi/ssl_transport_security.cc

src/core/tsi/ssl_transport_security.h

src/cpp/thread_manager/thread_manager.h

src/csharp/Grpc.Core/Internal/CallSafeHandle.cs

src/csharp/Grpc.Core/Internal/DefaultObjectPool.cs

src/objective-c/RxLibrary/GRXWriteable.h

src/php/composer.json

src/php/lib/Grpc/BidiStreamingCall.php

src/python/grpcio/grpc/_cython/_cygrpc/aio/call.pyx.pxi

src/python/grpcio/grpc/_cython/_cygrpc/grpc_string.pyx.pxi

src/python/grpcio_tests/tests/qps/benchmark_client.py

src/ruby/end2end/channel_closing_driver.rb

src/ruby/ext/grpc/rb_call.c

src/ruby/lib/grpc/generic/bidi_call.rb

src/ruby/lib/grpc/generic/rpc_server.rb

src/ruby/spec/google_rpc_status_utils_spec.rb

templates/Makefile.template

templates/src/php/composer.json.template