Do not change or generate README.md after running rspec (#8629)

* Do not change or generate README.md after running rspec

* Mock FastlaneCore::Env to skip generating docs

* Do not change existing code in lane_manager_spec

* Feedback addressed

* Fix rubocop error by extracting method

fastlane/lib/fastlane/lane_manager.rb

@@ -61,7 +61,7 @@ def self.cruise_lane(platform, lane, parameters = nil, env = nil)
       end
 
       # After running the lanes, since skip_docs might be somewhere in-between
-      Fastlane::DocsGenerator.run(ff) unless FastlaneCore::Env.truthy?("FASTLANE_SKIP_DOCS")
+      Fastlane::DocsGenerator.run(ff) unless skip_docs?
 
       duration = ((Time.now - started) / 60.0).round
 
@@ -70,6 +70,10 @@ def self.cruise_lane(platform, lane, parameters = nil, env = nil)
       return ff
     end
 
+    def self.skip_docs?
+      Helper.test? || FastlaneCore::Env.truthy?("FASTLANE_SKIP_DOCS")
+    end
+
     # All the finishing up that needs to be done
     def self.finish_fastlane(ff, duration, error)
       ff.runner.did_finish