ci: Remove MESON_TEST_MAX_PROCESSES

This variable was introduced to avoid spurious and flaky
issues where the CI would fail to spawn threads and exit.

I am confident this should be fixed by [1] so let's remove
this and see how it goes again.

MESON_TEST_MAX_PROCESSES in .gitlab-ci/run-tests.sh was left
in place however now it defaults to number_cpus rather than 1.

[1] https://gitlab.gnome.org/Infrastructure/ansible/-/merge_requests/27

.gitlab-ci.yml

@@ -26,7 +26,6 @@ variables:
   BACKEND_FLAGS: "-Dx11-backend=true -Dwayland-backend=true -Dbroadway-backend=true"
   FEATURE_FLAGS: "-Dvulkan=enabled -Dcloudproviders=enabled -Dbuild-testsuite=true -Dintrospection=enabled"
   MESON_TEST_TIMEOUT_MULTIPLIER: 3
-  MESON_TEST_MAX_PROCESSES: 8
   FEDORA_IMAGE: "registry.gitlab.gnome.org/gnome/gtk/fedora:v52"
 
 workflow:
@@ -398,8 +397,6 @@ asan-build:
   tags: [ asan ]
   stage: analysis
   needs: []
-  variables:
-    MESON_TEST_MAX_PROCESSES: 4
   script:
     - export PATH="$HOME/.local/bin:$PATH"
     - CC=clang meson setup

.gitlab-ci/run-tests.sh

@@ -8,7 +8,7 @@ builddir=$1
 setup=$2
 suite=$3
 multiplier=${MESON_TEST_TIMEOUT_MULTIPLIER:-1}
-n_processes=${MESON_TEST_MAX_PROCESSES:-1}
+n_processes=${MESON_TEST_MAX_PROCESSES:-$(nproc)}
 
 # Ignore memory leaks lower in dependencies
 export LSAN_OPTIONS=suppressions=$srcdir/lsan.supp:print_suppressions=0:detect_leaks=0:allocator_may_return_null=1:symbolize=1