ci: Fix macOS brew install command

Details: Homebrew/discussions#691

bitcoin/bitcoin#21663 (1/1)

Conflicts: .cirrus.yml; had to remove libnatpnp which was added upstream
 in bitcoin/bitcoin#18077 which is a much larger
 PR that we are NOT backporting.

.cirrus.yml

@@ -144,8 +144,9 @@ task:
 
 task:
   name: 'macOS 11 native [gui] [no depends]'
-  macos_brew_addon_script:
-    - brew install boost libevent berkeley-db4 qt miniupnpc ccache zeromq qrencode sqlite libtool automake pkg-config gnu-getopt
+  brew_install_script:
+    - brew update
+    - brew install boost libevent berkeley-db4 qt@5 miniupnpc ccache zeromq qrencode sqlite libtool automake pkg-config gnu-getopt
   << : *GLOBAL_TASK_TEMPLATE
   osx_instance:
     # Use latest image, but hardcode version to avoid silent upgrades (and breaks)