Update similarIssues.yml to have a lower tolerance (microsoft#16530)

The tolerance value for a similar repo was changed from 0.8 to 0.75.

This is because I changed the backend service for this to use pinecone
instead of Azure AI search (see here
craigloewen-msft/GitGudIssues@f72fa59
) and the metric changed as a result of that. They are slightly lower
than they were before, so this should offset that.

.github/workflows/similarIssues.yml

@@ -15,7 +15,7 @@ jobs:
         with:
           issuetitle: ${{ github.event.issue.title }}
           repo: ${{ github.repository }}
-          similaritytolerance: "0.8"
+          similaritytolerance: "0.75"
   add-comment:
     needs: getSimilarIssues
     runs-on: ubuntu-latest