doc: Fix pg_stat_autovacuum_scores descriptions.

doc: Fix pg_stat_autovacuum_scores descriptions.

The descriptions of the component scores state that values greater
than or equal to the corresponding weight parameter mean autovacuum
will process the table.  However, since the code that determines
whether to vacuum or analyze a table actually checks whether the
threshold is exceeded, it's more accurate to say "greater than"
there.

Author: Chao Li <li.evan.chao@gmail.com>
Reviewed-by: Sami Imseih <samimseih@gmail.com>
Discussion: https://postgr.es/m/E3ABDC6B-80CA-4C37-BA0B-A519D49F4C66%40gmail.com
Backpatch-through: 19