CI: fix even more brokenness in the macos CI

Commit 191449f has numerous issues, and
being completely invalid yml syntax was just the tip of the iceberg.

In this case, it fails the github schema, which requires that env be
adjunct to a job or step definition, rather than its own thing. It did
not even make sense in context, since the purpose of the variable is to
modify brew.

Fixes: mesonbuild#12644
Fixes: mesonbuild#12681

.github/workflows/macos.yml

@@ -101,7 +101,6 @@ jobs:
         CPPFLAGS: "-I/usr/local/include"
         LDFLAGS: "-L/usr/local/lib"
         MESON_ARGS: --unity=${{ matrix.unity }}
-        HOMEBREW_NO_AUTO_UPDATE: 1
         CI: 1
         # These cannot evaluate anything, so we cannot set PATH or SDKROOT here
       run: |
@@ -124,13 +123,13 @@ jobs:
 
   Qt4macos:
     runs-on: macos-latest
+    env:
+      HOMEBREW_NO_AUTO_UPDATE: 1
     steps:
     - uses: actions/checkout@v3
     - uses: actions/setup-python@v4
       with:
         python-version: '3.x'
-    - env:
-        HOMEBREW_NO_AUTO_UPDATE: 1
     - run: python -m pip install -e .
     - run: brew install pkg-config ninja gcc
     - run: brew tap cartr/qt4