pgsql: doc: Fix description about pg_stat_statements.track_planning.

doc: Fix description about pg_stat_statements.track_planning.

This commit fixes wrong wording like "a fewer kinds"
in the description about track_planning option.

Back-patch to v13 where pg_stat_statements.track_planning was added.

Author: Justin Pryzby
Reviewed-by: Julien Rouhaud, Fujii Masao
Discussion: https://postgr.es/m/20210418233615.GB7256@telsasoft.com

Branch
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REL_13_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/306c5e05e20fe37fcfe7dcde3ce4677b05a25285

Modified Files
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doc/src/sgml/pgstatstatements.sgml | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)