Bump hacking to 7.0.0

This bumps the hacking library, which is used to enforce OpenStack code
guidelines, to the latest released version. No code changes are required
to pass checks with this version.

Change-Id: I05ab9cb5db5c30cf537476cb494f707338ea67e9

test-requirements.txt

@@ -6,7 +6,7 @@ ansible-lint>=3.0.0,!=4.3.0 # MIT
 bashate>=0.2 # Apache-2.0
 coverage>=4.0 # Apache-2.0
 doc8 # Apache-2.0
-hacking>=6.1.0,<6.2.0 # Apache-2.0
+hacking>=7.0.0,<7.1.0 # Apache-2.0
 oslotest>=1.10.0 # Apache-2.0
 stestr # Apache-2.0
 yamllint # GPLv3