[REF] packaging: debian: depend on python-babel

Before this patch, the debian package depends on `python-pybabel`.
According to the documentation, this is a dummy package for transition
from `python-pybabel` to `python-babel`[1].

This dummy package has thus been removed in debian stretch in favor of
`python-babel`, and the odoo package is thus not installable in debian
stretch.

To fix this, we depend directly on `python-babel`, which is available in
all debian releases[2].

Closes #13905

[1] https://packages.debian.org/jessie/python-pybabel
[2] https://packages.debian.org/jessie/python-babel

debian/control

@@ -16,6 +16,7 @@ Depends:
  adduser,
  postgresql-client,
  python,
+ python-babel,
  python-dateutil,
  python-decorator,
  python-docutils,
@@ -31,7 +32,6 @@ Depends:
  python-passlib,
  python-psutil,
  python-psycopg2,
- python-pybabel,
  python-pychart,
  python-pydot,
  python-pyparsing,

setup/package.dfdebian

@@ -20,6 +20,7 @@ RUN apt-get update -qq &&  \
 		postgresql \
 		postgresql-client \
 		python \
+		python-babel \
 		python-dateutil \
 		python-decorator \
 		python-docutils \
@@ -35,7 +36,6 @@ RUN apt-get update -qq &&  \
 		python-passlib \
 		python-psutil \
 		python-psycopg2 \
-		python-pybabel \
 		python-pychart \
 		python-pydot \
 		python-pyparsing \