examples/simple_sniffer: only enable apptrace if JTAG is selected

Fixes compilation of this example on esp32c3, where apptrace is not
yet supported.

examples/wifi/simple_sniffer/main/Kconfig.projbuild

@@ -20,6 +20,7 @@ menu "Example Configuration"
                 Store pcap file to SD card.
         config SNIFFER_PCAP_DESTINATION_JTAG
             bool "JTAG (App Trace)"
+            select APPTRACE_DEST_TRAX
             help
                 Store pcap file to host via JTAG interface.
     endchoice

examples/wifi/simple_sniffer/sdkconfig.defaults

@@ -19,7 +19,3 @@ CONFIG_ESPTOOLPY_FLASHSIZE_4MB=y
 # FatFS
 CONFIG_FATFS_LFN_HEAP=y
 CONFIG_FATFS_MAX_LFN=31
-
-# App trace
-CONFIG_APPTRACE_DEST_TRAX=y
-CONFIG_APPTRACE_ENABLE=y