Fix linter on return statements

[ChloePlanet]

Please do not post any internal, closed source snippets on this public issue tracker!

Description

These two return statements below should be failed but they didn't.

return ok <: 200
return 200 ok

Reference: https://github.com/anz-bank/sysl/blob/master/pkg/parse/tests/lint_return.sysl

Steps to Reproduce

return ok <: 200

1. test.sysl file:

MobileApp:
  Name:
    return ok <: 200

2. $ sysl validate --root . test.sysl -v

return 200 ok

1. test.sysl file:

MobileApp:
  Name:
    return 200 ok

2. $ sysl validate --root . test.sysl -v

Expected behavior

no warnings

Actual behavior

WARN[0000] lint test.sysl:3:4: 'return ok <: 200' not supported, use 'return 200' instead

WARN[0000] lint test.sysl:3:4: 'return 200 ok' not supported, use 'return 200' instead

Your Environment

$ sysl info
Build:
  Version      : DIRTY-44179172f0a84093ce0e736a420176df9ea9301a (from v0.179.0)
  Git Commit   : 44179172f0a84093ce0e736a420176df9ea9301a
  Date         : 2020-08-13T02:24:17Z
  Go Version   : go1.13 darwin/amd64
  OS           : darwin/amd64