Update the Xcode version number in Kokoro (#7202) (#7203)
Update the Xcode version number in Kokoro (#7202) (#7203)

Currently all of our MacOS tests are failing with the error: "autom4te: need GNU m4 1.4 or later: /usr/bin/m4". This is likely to be happening because Kokoro has updated their Xcode version to 11.3.
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