logger.conf.sample: add missing comment mark

Add missing comment mark from stock configuration.

ASTERISK-29123 #close

Change-Id: I4f94eb4544166bca8af4c17fd11edee3c6980620

configs/samples/logger.conf.sample

@@ -112,7 +112,7 @@
 ;   - [plain]   - The plain formatter, this outputs log messages using a
 ;                 human readable format with the addition of function name
 ;                 and line number. No color escape codes are ever printed
-                  nor are verbose messages treated specially.
+;                 nor are verbose messages treated specially.
 ;   - [json]    - Log the output in JSON. Note that JSON formatted log entries,
 ;                 if specified for a logger type of 'console', will be formatted
 ;                 per the 'default' formatter for log messages of type VERBOSE.