[Chapel Merge] Add warnings to the documentation of symbols depre

Branch: refs/heads/main
Revision: f9b663d
Author: lydia-duncan
Log Message:

Merge pull request #18415 from lydia-duncan/docBigIntDep

Add warnings to the documentation of symbols deprecated with the keyword today
[reviewed by @e-kayrakli]

We were worried about how close it was to the release when making the change to
generate such documentation warnings automatically, so add them explicitly for
now (and future releases will not require the explicit step)

Double checked the built docs

Modified Files:
M modules/standard/BigInteger.chpl

Compare: https://github.com/chapel-lang/chapel/compare/ab40f4a10d30...f9b663de25f0