pgsql: Make spelling of cancelled/cancellation consistent

Make spelling of cancelled/cancellation consistent

This fixes places where words derived from cancel were not using their
common en-US ugly^H^H^H^Hspelling.

Author: Jelte Fennema-Nio <postgres@jeltef.nl>
Reported-by: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://postgr.es/m/CA+hUKG+Lrq+ty6yWXF5572qNQ8KwxGwG5n4fsEcCUap685nWvQ@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/8c9da1441df18bd609f025778e8349873a3e9bbd

Modified Files
--------------
doc/src/sgml/event-trigger.sgml                               | 2 +-
doc/src/sgml/libpq.sgml                                       | 2 +-
src/backend/storage/lmgr/proc.c                               | 2 +-
src/test/isolation/specs/detach-partition-concurrently-4.spec | 2 +-
src/test/recovery/t/001_stream_rep.pl                         | 2 +-
5 files changed, 5 insertions(+), 5 deletions(-)