Pin grpcio to 1.38.0

Author: lamhoangtung

requirements.txt

@@ -22,7 +22,7 @@ uvloop==0.14.0; sys_platform != 'win32' and python_version == '3.6'
 uvloop>=0.14.0; sys_platform != 'win32' and python_version >= '3.7'
 Werkzeug>=1.0.1
 httpx==0.18.2
-grpcio
+grpcio==1.38.0
 protobuf>=3.10.0
 boto3>=1.16.43
 pyyaml>=5.3.1