injection_points: pass enable_injection_points to the TAP test under meson

The new TAP test guards on $ENV{enable_injection_points}, which the make
build exports but the meson tap env did not set.  Under "use warnings
FATAL => 'all'" the resulting uninitialized-value warning aborts the test
before it can plan, so it failed on all meson platforms.  Set the variable in
the tap env like the other injection-point-using modules do.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: x4m

src/test/modules/injection_points/meson.build

@@ -43,6 +43,7 @@ tests += {
   'bd': meson.current_build_dir(),
   'tap': {
     'env': {
+      'enable_injection_points': get_option('injection_points') ? 'yes' : 'no',
       'INJECTION_POINTS_STATE': injection_points_state.full_path(),
     },
     'tests': [