bug #3979 removed invalid processors option (ricoli)

This PR was submitted for the 2.5 branch but it was merged into the 2.3 branch instead (closes #3979).

Discussion
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removed invalid processors option

As per symfony/monolog-bundle#77

Commits
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a462258 removed invalid processors option

Author: weaverryan

reference/configuration/monolog.rst

@@ -21,8 +21,6 @@ Full default Configuration
                     level:               ERROR
                     bubble:              false
                     formatter:           my_formatter
-                    processors:
-                        - some_callable
                 main:
                     type:                fingers_crossed
                     action_level:        WARNING