pgsql: Correct some uses of e.g. and i.e. in message strings and docume

Correct some uses of e.g. and i.e. in message strings and documentation

E.g. means "for example" and i.e. means "that is". Fix a couple uses
that don't match the intended meaning.

Kyotaro Horiguchi

Reviewed by Junwang Zhao and Aleksander Alekseev, with one addition by me
Discussion: https://www.postgresql.org/message-id/flat/20220713.180943.589079824955875739.horikyota.ntt%40gmail.com

This is a backpatch of 82785effc0 to v15

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/895723473ed8060a2afb50232a724471ae6743a2

Modified Files
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doc/src/sgml/ecpg.sgml     | 2 +-
src/bin/pg_upgrade/check.c | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)