minor #9957 Fixed minor typo (axzx)

This PR was submitted for the 4.1 branch but it was merged into the 2.8 branch instead (closes #9957).

Discussion
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Fixed minor typo

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Commits
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b464b31 Fixed typo

Author: javiereguiluz

logging/monolog_email.rst

@@ -17,7 +17,7 @@ it is broken down.
         # app/config/config_prod.yml
         monolog:
             handlers:
-                mail:
+                main:
                     type:         fingers_crossed
                     # 500 errors are logged at the critical level
                     action_level: critical