add pr number to changelog

Author: kachristensen

CHANGELOG.md

@@ -6,7 +6,7 @@ ENHANCEMENTS:
 BUG FIXES:
 * Fix error while importing monitor having timeZone as `null` in the Email notification object. (GH-637)
 * Fix perpetual diff in Extraction Rules by normalizing the parse expression.
-* Fix `resource_sumologic_cse_match_list` timing out when updating match list items
+* Fix `resource_sumologic_cse_match_list` timing out when updating match list items (GH-640)
 
 ## 2.28.3 (March 5, 2024)