probably mispelled property in pcap

In the pcap section, the documentation talks about the "mac_enable" property.
This property is not in the actual properties of the [pcap] section.
I thought it would be more probable to forget about the documentation property rather than the actual property name.
For this reason, I have changed the documentation from "mac_enable" to "enable".

srsenb/enb.conf.example

@@ -106,7 +106,7 @@ rx_gain = 40
 # To use the dissector, edit the preferences for DLT_USER to 
 # add an entry with DLT=150, Payload Protocol=s1ap.
 #
-# mac_enable:    Enable MAC layer packet captures (true/false)
+# enable:        Enable MAC layer packet captures (true/false)
 # filename:      File path to use for LTE MAC packet captures
 # nr_filename:   File path to use for NR MAC packet captures
 # s1ap_enable:   Enable or disable the PCAP.