Fix memory leak in PDU Session Setup Request decoding

* aper_decode allocates memory for for local pointer `pdusessionTransfer`, in `decodePDUSessionResourceSetup`
* this memory seems not to be freed but its members are by:
  `ASN_STRUCT_FREE_CONTENTS_ONLY(asn_DEF_NGAP_PDUSessionResourceSetupRequestTransfer,pdusessionTransfer);`
  which btw in its header says: "AVOID using it in the application code; Use a safer ASN_STRUCT_RESET() instead"
* the following mem leak was detected by ASAN:

```
Direct leak of 72 byte(s) in 1 object(s) allocated from:
   *0 0x7ffff74b4a57 in __interceptor_calloc /src/libsanitizer/asan/asan_malloc_linux.cpp:154
   *1 0x55555cb306df in SEQUENCE_decode_aper /cmake_targets/ran_build/build/openair2/RRC/LTE/MESSAGES/constr_SEQUENCE_aper.c:36
   *2 0x55555ca9fa28 in aper_decode /cmake_targets/ran_build/build/openair2/RRC/LTE/MESSAGES/aper_decoder.c:78
   *3 0x55555b99bae6 in decodePDUSessionResourceSetup /openair2/RRC/NR/rrc_gNB_NGAP.c:273
   *4 0x55555b99fec2 in trigger_bearer_setup /openair2/RRC/NR/rrc_gNB_NGAP.c:357
   *5 0x55555b9b54bf in rrc_gNB_process_NGAP_PDUSESSION_SETUP_REQ /openair2/RRC/NR/rrc_gNB_NGAP.c:830
   *6 0x55555b936871 in rrc_gnb_task /openair2/RRC/NR/rrc_gNB.c:2428
   *7 0x7ffff5e94ac2 in start_thread nptl/pthread_create.c:442
```

* This commit replaces ASN_STRUCT_FREE_CONTENTS_ONLY with ASN_STRUCT_FREE, which will free the memory allocated for the entire struct and its members

openair2/RRC/NR/rrc_gNB_NGAP.c

@@ -335,7 +335,7 @@ static int decodePDUSessionResourceSetup(pdusession_t *session)
         return -1;
     }
   }
-  ASN_STRUCT_FREE_CONTENTS_ONLY(asn_DEF_NGAP_PDUSessionResourceSetupRequestTransfer,pdusessionTransfer );
+  ASN_STRUCT_FREE(asn_DEF_NGAP_PDUSessionResourceSetupRequestTransfer, pdusessionTransfer);
 
   return 0;
 }