rpcgen: Don't skip all tests when pytest is missing

Some of the files used by test_demo.c can only be regenerated
when pytest is present, but we have pre-generated copies in the
repository, so overall we just need the C compiler to build and
run that specific test program.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

scripts/rpcgen/meson.build

@@ -1,8 +1,7 @@
 subdir('rpcgen')
+subdir('tests')
 
 if pytest_prog.found()
-    subdir('tests')
-
     test(
         'rpcgen-pytest',
         python3_prog,