doc: Fix typo in rule-system view example

doc: Fix typo in rule-system view example

Commit dcb00495236 accidentally changed the final expanded query's
condition to > 2 while rewriting the example into SQL operator notation.

The original query and the preceding rewritten forms all use >= 2,
and view expansion should preserve that qualification. This commit
changes the final condition from > 2 to >= 2.

Backpatch to all supported versions.

Reported-by: Yaroslav Saburov <y.saburov@gmail.com>
Author: Fujii Masao <masao.fujii@gmail.com>
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Discussion: https://postgr.es/m/178248467618.108999.9966122434342474006@wrigleys.postgresql.org
Backpatch-through: 14