Bump flake8 and fix resulting lint errors

Remove unecessary global declaration in core.py that failed on new
flake8 lint. Pinning on paramiko was removed as older versions use
pycrypto which is incompatible with Python 3.12.

Change-Id: I2811788129fd2b21416d3c64fff870c1542bedc0
Signed-off-by: Myles Penner <myles.penner@canonical.com>

charms_openstack/charm/core.py

@@ -334,7 +334,6 @@ class BaseOpenStackCharmMeta(type):
         :param mro: tuple of base classes.
         :param members: dictionary of name to class attribute (f, p, a, etc.)
         """
-        global _releases
         # Do not attempt to calculate the release for an abstract class
         if members.get('abstract_class', False):
             return

test-requirements.txt

@@ -2,8 +2,8 @@ simplejson
 requests
 httpretty
 pep8
-flake8>=2.2.4
+flake8>=7.1.1
 stestr
-paramiko<2.0
+paramiko
 charms.reactive
 coverage>=3.6