pgsql: Fix documentation of pgrowlocks using "lock_type" instead of "mo

Fix documentation of pgrowlocks using "lock_type" instead of "modes"

The example used in the documentation is outdated as well. This is an
oversight from 0ac5ad5, which bumped up pgrowlocks but forgot some bits
of the documentation.

Reported-by: Chris Wilson
Discussion: /messages/by-id/153838692816.2950.12001142346234155699@wrigleys.postgresql.org
Backpatch-through: 9.3

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/80810ca629c159191387f677b368a0551bbf2351

Modified Files
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doc/src/sgml/pgrowlocks.sgml | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)