Remove unnecessary "inline" marker introduced in commit 4be058fe9.

Remove unnecessary "inline" marker introduced in commit 4be058fe9.

Some of our older buildfarm members bleat about this coding,
along the lines of

prepjointree.c:112: warning: 'get_result_relid' declared inline after being called
prepjointree.c:112: warning: previous declaration of 'get_result_relid' was here

Modern compilers will probably inline this function without being
prompted, so rather than move the function, let's just drop the
marking.