ci: Update already installed Arch Linux packages

We seem to be installing a version of `libstdc++` that's incompatible
with the version of glibc that the image shipped with.

The Arch Linux wiki says to avoid using `pacman -Sy` and to instead use
`pacman -Syu`. Issues like this are probably why.

Signed-off-by: Matt Wozniski <mwozniski@bloomberg.net>

.github/workflows/build_wheels.yml

@@ -235,7 +235,7 @@ jobs:
           path: dist
       - name: Set up dependencies
         run: |
-          pacman -Sy --noconfirm \
+          pacman -Syu --noconfirm \
             gdb \
             gcc \
             file \