pgsql: Run nbtree test module tests under autoconf builds

Run nbtree test module tests under autoconf builds

Commit 1e4e5783e added the src/test/modules/nbtree test module, but only
registered it in the meson build, not in the module list in
src/test/modules/Makefile. As a result, autoconf builds never ran the
module's tests.

To fix, add the module to the Makefile's lists of
injection-point-dependent modules.

Oversight in commit 1e4e5783e.

Author: Peter Geoghegan <pg(at)bowt(dot)ie>
Reviewed-by: Michael Paquiër <michael(at)paquier(dot)xyz>
Discussion: https://postgr.es/m/CAH2-Wz=JchiD5ksiT35p8Ar02gaNv8_y6w2wBAST+Zzen-eNjw@mail.gmail.com
Backpatch-through: 19

Branch
------
REL_19_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/bd6ca6f852694a8a0f52db748ff8badec4223c8f

Modified Files
--------------
src/test/modules/Makefile | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)