[Chapel Merge] Add missing variable in `chpl-language-server`

Branch: refs/heads/main
Revision: b11b8901e3c9925a26c03b07ffa8d32b3ceae322
Author: jabraham17
Link: Add missing variable in `chpl-language-server` by jabraham17 · Pull Request #25221 · chapel-lang/chapel · GitHub
Log Message:
Add missing variable in chpl-language-server (#25221)

Followup to Make `chplcheck` available from `chpl-language-server` by jabraham17 · Pull Request #25214 · chapel-lang/chapel · GitHub, fixes a
missing variable forgotten when applying reviewer feedback

Tested with make test-cls

[Reviewed by @DanilaFe and @lydia-duncan ]

Compare: Comparing 09ad1a621a00c49f546f08e3c3c1980c860b901f...968c10c3f25364a6fff78590044acf41b266df44 · chapel-lang/chapel · GitHub

M doc/rst/tools/chpl-language-server/chpl-language-server.rst
M tools/chpl-language-server/src/chpl-language-server.py