Pkg tests puts an outdated copy of `General` in `usr/share/registries`

[Keno]

Before:

keno@demeter2:~$ ls -la julia/usr/share/julia/registries
total 0
drwxrwxr-x 1 keno keno   0 Jul  4 18:41 .
drwxrwxr-x 1 keno keno 180 Jul  4 18:29 ..

Then

keno@demeter2:~/julia$ make test-Pkg
Whitespace check found no issues.
This build contains [GPL-2.0+] libs: libcholmod librbio libspqr libumfpack
    JULIA test/Pkg
Running parallel tests with:
  getpid() = 3098280
  nworkers() = 1
  nthreads() = 1
  Sys.CPU_THREADS = 64
  Sys.total_memory() = 755.458 GiB
  Sys.free_memory() = 727.929 GiB

Test  (Worker) | Time (s) | GC (s) | GC % | Alloc (MB) | RSS (MB)
Pkg        (1) |        started at 2024-07-04T18:41:40.414

and shortly thereafter:

total 7608
drwxrwxr-x 1 keno keno      52 Jul  4 18:41 .
drwxrwxr-x 1 keno keno     180 Jul  4 18:29 ..
-rw-rw-r-- 1 keno keno 7786491 Jul  4 18:41 General.tar.gz
-rw-rw-r-- 1 keno keno     129 Jul  4 18:41 General.toml

This is problematic because:

1. This copy of General doesn't get updated
2. Having this copy of General present prevents julia from installing the ~/.julia/registries copy (if not already present)
3. Having only this copy is confusing (#3939)