Unpin pip version installed in build_python.sh
Unpin pip version installed in build_python.sh

Fix for issue #14815. Pinning to 9.0.3 doesn't work because pip fails to
recognize that as a valid version. Newer versions of pip have a fallback
on macOS to use SecureTransport instead of their outdated OpenSSL that
doesn't support TLSv1.2.

stanley-cheung/grpc,ejona86/grpc,vjpai/grpc,nicolasnoble/grpc,dgquintas/grpc,jtattermusch/grpc,chrisdunelm/grpc,grpc/grpc,muxi/grpc,grpc/grpc,grpc/grpc,vjpai/grpc,grpc/grpc,vjpai/grpc,pszemus/grpc,firebase/grpc,grpc/grpc,kpayson64/grpc,sreecha/grpc,dgquintas/grpc,sreecha/grpc,firebase/grpc,pszemus/grpc,mehrdada/grpc,sreecha/grpc,jboeuf/grpc,carl-mastrangelo/grpc,carl-mastrangelo/grpc,ctiller/grpc,vjpai/grpc,vjpai/grpc,stanley-cheung/grpc,carl-mastrangelo/grpc,chrisdunelm/grpc,ncteisen/grpc,kpayson64/grpc,stanley-cheung/grpc,thinkerou/grpc,thinkerou/grpc,stanley-cheung/grpc,simonkuang/grpc,sreecha/grpc,kpayson64/grpc,pszemus/grpc,grpc/grpc,muxi/grpc,pszemus/grpc,donnadionne/grpc,sreecha/grpc,firebase/grpc,mehrdada/grpc,ncteisen/grpc,firebase/grpc,ctiller/grpc,thinkerou/grpc,donnadionne/grpc,stanley-cheung/grpc,Vizerai/grpc,donnadionne/grpc,dgquintas/grpc,vjpai/grpc,mehrdada/grpc,ejona86/grpc,jboeuf/grpc,nicolasnoble/grpc,ejona86/grpc,ncteisen/grpc,thinkerou/grpc,grpc/grpc,muxi/grpc,pszemus/grpc,kpayson64/grpc,chrisdunelm/grpc,Vizerai/grpc,nicolasnoble/grpc,jboeuf/grpc,nicolasnoble/grpc,dgquintas/grpc,mehrdada/grpc,ctiller/grpc,carl-mastrangelo/grpc,mehrdada/grpc,dgquintas/grpc,firebase/grpc,nicolasnoble/grpc,ctiller/grpc,mehrdada/grpc,ncteisen/grpc,ctiller/grpc,firebase/grpc,thinkerou/grpc,mehrdada/grpc,stanley-cheung/grpc,chrisdunelm/grpc,simonkuang/grpc,dgquintas/grpc,ejona86/grpc,kpayson64/grpc,jboeuf/grpc,stanley-cheung/grpc,ncteisen/grpc,ejona86/grpc,thinkerou/grpc,thinkerou/grpc,chrisdunelm/grpc,jboeuf/grpc,muxi/grpc,ncteisen/grpc,vjpai/grpc,ctiller/grpc,vjpai/grpc,muxi/grpc,thinkerou/grpc,jboeuf/grpc,donnadionne/grpc,carl-mastrangelo/grpc,ejona86/grpc,mehrdada/grpc,jtattermusch/grpc,firebase/grpc,donnadionne/grpc,firebase/grpc,ctiller/grpc,simonkuang/grpc,ctiller/grpc,grpc/grpc,donnadionne/grpc,muxi/grpc,thinkerou/grpc,pszemus/grpc,stanley-cheung/grpc,dgquintas/grpc,sreecha/grpc,jboeuf/grpc,donnadionne/grpc,stanley-cheung/grpc,sreecha/grpc,chrisdunelm/grpc,nicolasnoble/grpc,stanley-cheung/grpc,simonkuang/grpc,dgquintas/grpc,firebase/grpc,donnadionne/grpc,carl-mastrangelo/grpc,nicolasnoble/grpc,ctiller/grpc,jtattermusch/grpc,kpayson64/grpc,grpc/grpc,chrisdunelm/grpc,jtattermusch/grpc,simonkuang/grpc,nicolasnoble/grpc,donnadionne/grpc,simonkuang/grpc,kpayson64/grpc,ncteisen/grpc,simonkuang/grpc,ncteisen/grpc,mehrdada/grpc,vjpai/grpc,chrisdunelm/grpc,simonkuang/grpc,jboeuf/grpc,kpayson64/grpc,pszemus/grpc,carl-mastrangelo/grpc,carl-mastrangelo/grpc,jtattermusch/grpc,Vizerai/grpc,sreecha/grpc,nicolasnoble/grpc,Vizerai/grpc,ejona86/grpc,ejona86/grpc,nicolasnoble/grpc,jtattermusch/grpc,muxi/grpc,grpc/grpc,ejona86/grpc,ctiller/grpc,ejona86/grpc,chrisdunelm/grpc,Vizerai/grpc,sreecha/grpc,muxi/grpc,carl-mastrangelo/grpc,vjpai/grpc,ejona86/grpc,Vizerai/grpc,thinkerou/grpc,carl-mastrangelo/grpc,grpc/grpc,kpayson64/grpc,dgquintas/grpc,muxi/grpc,donnadionne/grpc,pszemus/grpc,Vizerai/grpc,jboeuf/grpc,pszemus/grpc,thinkerou/grpc,sreecha/grpc,Vizerai/grpc,ctiller/grpc,grpc/grpc,jboeuf/grpc,dgquintas/grpc,firebase/grpc,Vizerai/grpc,sreecha/grpc,muxi/grpc,jtattermusch/grpc,ejona86/grpc,jtattermusch/grpc,stanley-cheung/grpc,stanley-cheung/grpc,mehrdada/grpc,pszemus/grpc,ncteisen/grpc,ncteisen/grpc,thinkerou/grpc,firebase/grpc,jboeuf/grpc,nicolasnoble/grpc,mehrdada/grpc,simonkuang/grpc,jtattermusch/grpc,firebase/grpc,vjpai/grpc,jtattermusch/grpc,vjpai/grpc,ncteisen/grpc,kpayson64/grpc,Vizerai/grpc,Vizerai/grpc,chrisdunelm/grpc,kpayson64/grpc,pszemus/grpc,nicolasnoble/grpc,ncteisen/grpc,muxi/grpc,ctiller/grpc,donnadionne/grpc,sreecha/grpc,chrisdunelm/grpc,dgquintas/grpc,jtattermusch/grpc,muxi/grpc,jboeuf/grpc,carl-mastrangelo/grpc,mehrdada/grpc,donnadionne/grpc,jtattermusch/grpc,pszemus/grpc,carl-mastrangelo/grpc