Fix a typo (s/an/a/) in the malware issue template (#8633)

Author: webknjaz

.github/ISSUE_TEMPLATE/malware-check.md

@@ -1,6 +1,6 @@
 ---
 name: Malware Check
-about: Contribute an new automated malware check to PyPI
+about: Contribute a new automated malware check to PyPI
 
 ---