Don't require simplecov in cucumber env.rb

MSP-11671

All features currently use aruba to run msfconsole in a separate process
and it is that child process that needs to load simplecov.  Changes
average runtime for `rake cucumber:boot` from (n=10) 122.21 seconds to
(n=13) 112.50 seconds (-7.50%).  Raw data:
https://docs.google.com/spreadsheets/d/1vCRi_38Go3Wfq670eDCXMTSSXL1blSbk6NQsgpOqfYw/edit?usp=sharing

Author: limhoff-r7

features/support/env.rb

@@ -1,5 +1,5 @@
-# Has to be the first file required so that all other files show coverage information
-require 'simplecov'
+# @note `require 'simplecov'` is not used here because all features currently use external `msfconsole` process, so only
+#   that child process needs to load 'simplecov'.
 
 # IMPORTANT: This file is generated by cucumber-rails - edit at your own peril.
 # It is recommended to regenerate this file in the future when you upgrade to a