ci: fix typo. (#523)

Author: dundargoc

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -16,7 +16,7 @@ body:
           required: true
         - label: I have searched the existing issues of lazy.nvim
           required: true
-        - label: I have searched the exsiting issues of plugins related to this issue
+        - label: I have searched the existing issues of plugins related to this issue
           required: true
   - type: input
     attributes: