build: try different ID for pip grype error.

The bare CVE id CVE-2018-20225 didn't work.  In the sarif output it
report id: CVE-2018-20225-pip, so try that.

Author: rouilj

.grype.yaml

@@ -1,4 +1,5 @@
 ignore:
   - vulnerability: CVE-2018-20225
     fix-state: not-fixed
-    
+  - vulnerability: CVE-2018-20225-pip
+    fix-state: not-fixed