fix: correct getindex(vi, ::Colon) docstring (#854)

[ArpanC6]

Closes #854

What was the problem?

The docstring for getindex(vi::AbstractVarInfo, ::Colon) incorrectly
stated that it returns values "in the support of its distribution(s)".
This is wrong - vi[:] actually returns the internally stored values,
which may be in transformed (linked) space if vi has been linked.

What did I fix?

Updated the docstring to correctly state that:

• vi[:] returns internal values which may be transformed
• For untransformed values use getindex_internal after calling invlink

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.35%. Comparing base (10a3651) to head (d3f7436).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1382   +/-   ##
=======================================
  Coverage   82.35%   82.35%           
=======================================
  Files          50       50           
  Lines        3531     3531           
=======================================
  Hits         2908     2908           
  Misses        623      623           

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[ArpanC6]

Hlw @yebai I've been contributing to DynamicPPL.jl and really enjoying it. With @penelopeysm moving on could you point me to someone who could review PRs going forward? I'd love to keep contributing.

Note: This PR addresses the docstring fix as mentioned in the issue. The larger fix of changing the behaviour of vi[:] to return untransformed values is a separate more involved task that is left for a future PR.