MNT fix GitHub pull request template link (scikit-learn#19009)

Author: harrismirza

PULL_REQUEST_TEMPLATE.md

@@ -1,6 +1,6 @@
 <!--
 Thanks for contributing a pull request! Please ensure you have taken a look at
-the contribution guidelines: https://github.com/scikit-learn/scikit-learn/blob/master/CONTRIBUTING.md#pull-request-checklist
+the contribution guidelines: https://github.com/scikit-learn/scikit-learn/blob/master/CONTRIBUTING.md
 -->
 
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