fix "--resolver global " needs network

[diqye]

issue: #5103

• [ x ] Any changes that could be relevant to users have been recorded in the ChangeLog.md
• [ x ] The documentation has been updated, if necessary.

Test case:

stack test   673 examples, 0 failures
stack --resolver global   is ok
stack --resolver nightly is ok
stack --resolver lts-14   is ok
stack --resolver lts-14.13 is ok

[qrilka]

Thanks @ppzzppz
Could you also add a changelog entry stating that global doesn't retrieve snapshots list from the internet anymore as it doesn't need it?

[diqye]

@qrilka Received. Thanks for review.

Could changeLog be written under "Changes since v2.1.3.1"?

Such as the following：

**Changes since v2.1.3.1**

Release notes:

Major changes:

Behavior changes:

Other enhancements:

* Remove warning for using Stack with GHC 8.8 and Cabal 3.0.
* `--resolver global` doesn't retrieve snapshots list from the internet beause doesn't need it

Bug fixes:

[qrilka]

Surely it's since v2.1.3.1 the question is whether it's an enhancement or a bug fix, I'm a bit more inclined to see it as a bug fix

[snoyberg]

Thanks!