Fix missing undefine in sort_template.h

All parameter macros are supposed to be undefined at the end of the
header. ST_CHECK_FOR_INTERRUPTS was forgotten, so could affect later
inclusions.

Thomas Munro

The patch set of which this is a part is discussed in
https://www.postgresql.org/message-id/CA%2BhUKGLPommgNw-SVwUGkw1YmTDwmJ5vSKO0kFnZfbRHtNFW5w%40mail.gmail.com

Author: j-naylor

src/include/lib/sort_template.h

@@ -407,6 +407,7 @@ ST_SORT(ST_ELEMENT_TYPE * data, size_t n
 #undef DO_SORT
 #undef DO_SWAP
 #undef DO_SWAPN
+#undef ST_CHECK_FOR_INTERRUPTS
 #undef ST_COMPARATOR_TYPE_NAME
 #undef ST_COMPARE
 #undef ST_COMPARE_ARG_TYPE