devel/Makefile: temporarily comment out py-subversion

The blocked commit to devel/py3c prevents dependent ports tp be built.
Disable this port until py3c is restored.

Reported by:	antoine
Approved by:	portmgr (implicit)

devel/Makefile

@@ -5338,7 +5338,7 @@
     SUBDIR += py-stringcase
     SUBDIR += py-structlog
     SUBDIR += py-subprocess-tee
-    SUBDIR += py-subversion
+#   SUBDIR += py-subversion
     SUBDIR += py-sure
     SUBDIR += py-swagger-spec-validator
     SUBDIR += py-synr