GHA: explicitly `brew update` before `brew install` with Linuxbrew

GHA: explicitly `brew update` before `brew install` with Linuxbrew

Fixing:
```
==> Installing openssl@3 dependency: ca-certificates
==> Pouring ca-certificates--2026-05-14.all.bottle.tar.gz
Error: undefined method '[]' for nil
/home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/utils/bottles.rb:127:in 'Utils::Bottles.load_tab'
/home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/formula_installer.rb:1507:in 'FormulaInstaller#pour'
[...]
/home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/brew.rb:114:in '<main>'
You have disabled automatic updates and have not updated today.
Do not report this issue until you've run `brew update` and tried again.
Error: Process completed with exit code 1.
```
Ref: https://github.com/curl/curl/actions/runs/25859030402/job/75984082148?pr=21607

Dropping `HOMEBREW_NO_AUTO_UPDATE=1` was not enough to fix it.

Closes #21608