changed severity of G-9020 to blocker

same reason as for G-9010, change of NLS settings
may lead to a unexpected behaviour, a bug

Author: PhilippSalvisberg

docs/4-language-usage/9-function-usage/g-9020.md

@@ -1,6 +1,6 @@
 # G-9020: Try to use a format model and NLS_NUMERIC_CHARACTERS in string to number conversion functions.
 
-!!! warning "Major"
+!!! bug "Blocker"
     Changeability, Maintainability, Reliability, Security, Testability
 
 ## Reason