poco: Remove unnecessary configuration

Darwin64 is an alias for Darwin64-clang, and likewise Darwin32 is an
alias for Darwin32-clang.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
poco 1.4.7p1

Closes #30637.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
poco: update 1.4.7p1 bottle.