minor #6700 Update monolog.rst (zhil)

This PR was submitted for the 3.1 branch but it was merged into the 2.7 branch instead (closes #6700).

Discussion
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Update monolog.rst

Default value for buffer_size is unlimited, which worth being mentioned

Commits
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c5a2d9e Update monolog.rst

Author: wouterj

reference/configuration/monolog.rst

@@ -27,7 +27,8 @@ Full Default Configuration
                 main:
                     type:                fingers_crossed
                     action_level:        WARNING
-                    buffer_size:         30
+                    # by default buffer_size is unlimited, which could generate huge logs in some cases.
+                    buffer_size:         0
                     handler:             custom
                 console:
                     type:                console
@@ -97,6 +98,7 @@ Full Default Configuration
                     type="fingers_crossed"
                     action-level="warning"
                     handler="custom"
+                    buffer-size="0"
                 />
                 <monolog:handler
                     name="console"