pgsql: Remove double quotes from the second column of wait_event_names.

Remove double quotes from the second column of wait_event_names.txt

The double quotes used for the wait event names are not required, as
the values quoted are made of single words. The files generated by
generate-wait_event_types.pl (pgstat_wait_event.c, wait_event_types.h
and wait_event_types.sgml) are exactly the same before and after this
commit, hence the wait event names and the enum elements have the same
names as before.

Discussion: https://postgr.es/m/ZK9S3jFEV1X797Ll@paquier.xyz

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/183a60a628fec074372e7a53d5006c18bd7a8e53

Modified Files
--------------
.../utils/activity/generate-wait_event_types.pl | 8 +-
src/backend/utils/activity/wait_event_names.txt | 492 ++++++++++-----------
2 files changed, 251 insertions(+), 249 deletions(-)