pgsql: Remove useless casts

Remove useless casts

Casting the argument of strVal() to (Value *) is useless, since
strVal() already does that.

Most code didn't do that anyway; this was apparently just a style that
snuck into certain files.

Reviewed-by: Dagfinn Ilmari Mannsåker 
Reviewed-by: Kyotaro Horiguchi 
Discussion: https://www.postgresql.org/message-id/flat/5ba6bc5b-3f95-04f2-2419-f8ddb4c046fb@enterprisedb.com

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/cbdf75bf8053f88bbae6b307f34ab057424a370f

Modified Files
--------------
src/backend/catalog/objectaddress.c | 20 ++++++++++----------
src/backend/commands/alter.c        | 16 ++++++++--------
src/backend/commands/comment.c      |  2 +-
src/backend/commands/dropcmds.c     | 16 ++++++++--------
src/backend/commands/statscmds.c    |  2 +-
5 files changed, 28 insertions(+), 28 deletions(-)