CI: Increase ccache size limit for serenity builds

Now that we only have 3 ccached builds on CI we can comfortably increase
the ccache size limit to get some free speed-up in CI.

.github/workflows/cmake.yml

@@ -109,12 +109,12 @@ jobs:
  - name: Show ccache stats before build and configure
  run: |
  # We only have 5 GiB of cache available *in total*. Beyond that, GitHub deletes caches.
- # Currently, we use about 130 MB for the two toolchains (i686 & x86_64), and four ccache caches:
- # Two with ALL_DEBUG (i686 & x86_64) and two with NORMAL_DEBUG (i686 & x86_64).
- # Therefore, using 1.25 GB or more per cache causes disaster.
+ # Currently, we use about 130 MB for the two toolchains (i686 & x86_64), and three ccache caches:
+ # One with ALL_DEBUG (i686) and two with NORMAL_DEBUG (i686 & x86_64).
+ # Therefore, using 1.6 GB or more per cache causes disaster.
  # Building from scratch fills the ccache cache from 0 to about 0.7 GB, and after compression it comes out to
- # about 0.25 GB, so 1.5 GB (0.5GB after compression) should be plenty, all while comfortly fitting in the cache.
- ccache -M 1500M
+ # about 0.25 GB, so 3 GB (1GB after compression) should be plenty, all while comfortably fitting in the cache.
+ ccache -M 3000M
  ccache -s
  - name: Create build directory
  run: |