Fold the constant splashFontCacheSize

As the cache is a std::array now, the constant is only used in a
single location.  Hence there is no need to keep it as a separate
name.
3 jobs for remove-unnecessary-nullptr-check-from-splash in 6 minutes and 38 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Build
passed #23948
build

00:03:06

passed #23176
build_clang_libcpp

00:03:31

failed #23175
build

00:00:10