[PATCH] Fix incorrect Spanish translation and remove obsolete FIXME comments

Hi all,

While reviewing the Spanish translation file (src/backend/po/es.po),
I found an incorrect translation in the message:

"physical replication slot \"%s\" exists, but \"wal_level\" < \"replica\""

The current translation refers to a logical replication slot
("replicación lógica"), which is incorrect in this context.
This patch corrects the translation to use "replicación física",
so that the message accurately reflects the original meaning.

In addition, I reviewed several FIXME comments present in the same
file, including comments referencing slot.c:779 and postmaster.c:835,
as well as notes questioning duplication and terminology (e.g.,
"snapbuild" and "snapshot"). After verifying the corresponding
source code and checking for message duplication, these comments
appear to be outdated translator notes that no longer apply to the
current codebase.

This patch removes those obsolete FIXME comments while keeping
the existing translations unchanged, except for the corrected
physical replication slot message described above.

The updated es.po file was validated using:

msgfmt -c -v es.po

which reports no format or consistency issues.

Patch attached.

Regards,
Vasuki M
C-DAC,Chennai