pgsql: Use "true" not "TRUE" in one ICU function call.

Use "true" not "TRUE" in one ICU function call.

This was evidently missed in commit 6337865f3, which generally did
s/TRUE/true/ everywhere.  It escaped notice up to now because ICU
versions before ICU 68 provided definitions of "TRUE" and "FALSE"
regardless.  With ICU 68, it fails to compile.

Per report from Condor.  Back-patch to v11 where 6337865f3 came in.
(I've not tested v10, where this call originated, but I imagine
it's fine since we defined TRUE in c.h back then.)

Discussion: https://postgr.es/m/7a6f3336165bfe3ca66abcda7966f9d0@stz-bg.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/ad84ecc98d7e2ad81567094b8a6910b5078927a7

Modified Files
--------------
src/backend/commands/collationcmds.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)