setup.py: temporary upper limit to prospector

* The latest release of prospector doesn't ship the with_* extras.
  See: landscapeio/prospector#545

Change-Id: I6092bf0d5cf2143d216d9bf6a06b166feaa14e1e

setup.py

@@ -24,7 +24,7 @@
         'pytest>=6.1.0',
     ],
     'prospector': [
-        'prospector[with_everything]>=0.12.4',
+        'prospector[with_everything]>=0.12.4,<=1.7.7',
         'pylint<2.15.7',  # Temporary upper limit for an upstream regression
         'pytest>=6.1.0',
     ],