pgsql: Remove unused configure variable.

Remove unused configure variable.

configure extracts TCL_SHLIB_LD_LIBS from tclConfig.sh, and puts the
value into Makefile.global, but then we never use it anywhere.  It
looks like I removed the only usage in cd75f94da, but didn't notice
that it was the only usage.  Might as well mop this up while we're
trying to get rid of unnecessary configure steps.

Discussion: https://postgr.es/m/2442359.1660835043@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/27f1774aac1f8ffe642b55e78dbe0b64ed082cc6

Modified Files
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configure              | 3 +--
configure.ac           | 1 -
src/Makefile.global.in | 1 -
3 files changed, 1 insertion(+), 4 deletions(-)