Syntax error in example of docs/3-coding-style/coding-style.md

[Philipp Salvisberg]

The example in the Coding Style chapter has a syntax error.

The formatter does not throw an error because SQLDev's parser can handle this syntax. However, db* CODECOP cannot and neither can the Oracle Database (it throws an "unknown command on line 1" error).

So, I suggest to add a create or replace to fix the issue.