package/python-avro: fix comment

A last-minute fixup when applying 5527266559d9 (package/python-avro:
don't refer to avro-c version variable) improperly duplicated the exact
same comment as in avro-c. Of course, we want to refer to avro-c from
python-avro...

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/python-avro/python-avro.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-# When updating the version, please also update python-avro
+# When updating the version, please also update avro-c
 PYTHON_AVRO_VERSION = 1.11.0
 PYTHON_AVRO_SITE = \
 	https://www-eu.apache.org/dist/avro/avro-$(PYTHON_AVRO_VERSION)/py