Run pgvector-clean before pgvector-setup

For some reason the pgvector compiled for PostgreSQL 13 was
being installed in the PostgreSQL 14 library path:

`tmp/loadable_libraries.txt` failed with:

```
could not load library "$libdir/vector": ERROR:  incompatible library "/Users/psj/.asdf/installs/postgres/14.9/lib/vector.so": version mismatch
DETAIL:  Server is version 14, library is version 13.
In database: gitlabhq_development_embedding
In database: gitlabhq_test_embedding
```

To avoid this problem, run `make pgvector-clean` before the `make
pgvector-setup`.