linux_and_macos.yml: Drop "brew update" to fix CI

As of the moment, package php comes pre-installed
and trying to apply mass-upgrades fails at php.

Author: hartwork

.github/workflows/linux_and_macos.yml

@@ -83,7 +83,6 @@ jobs:
         if: runner.os == 'macOS'
         run: |-
           set -x
-          brew update
           brew install \
             autoconf-archive \
             automake \