Do not update brew formulae upon install

Change-Id: Ifc726b9456f4643b77e9f2eefc1bd37efbc50150

.github/workflows/macos.yml

diff --git a/.github/workflows/macos.yml b/.github/workflows/macos.yml
index dcb6975..398ecf2 100644
--- a/.github/workflows/macos.yml
+++ b/.github/workflows/macos.yml
@@ -33,7 +33,6 @@
       - name: Setup Dependencies (iOS)
         if: matrix.target == 'ios'
         run: |
-          brew update
           brew install \
             ccache \
             eigen \
@@ -42,7 +41,6 @@
       - name: Setup Dependencies (Host)
         if: matrix.target == 'host'
         run: |
-          brew update
           brew install \
             ccache \
             eigen \