CommonLibs: remove unused *trx in cfg[_no]_ctr_error_threshold_cmd

Compilation fails when building with -Wall and -Werror:

trx_vty.c: In function ‘cfg_ctr_error_threshold’:
trx_vty.c:469:18: error: unused variable ‘trx’ [-Werror=unused-variable]
  struct trx_ctx *trx = trx_from_vty(vty);
                  ^~~
trx_vty.c: In function ‘cfg_no_ctr_error_threshold’:
trx_vty.c:501:18: error: unused variable ‘trx’ [-Werror=unused-variable]
  struct trx_ctx *trx = trx_from_vty(vty);
                  ^~~

Change-Id: I3d74c3f38aa03608a32b9dee472e49236543c87f
diff --git a/CommonLibs/trx_vty.c b/CommonLibs/trx_vty.c
index 2b0ba71..ba55f92 100644
--- a/CommonLibs/trx_vty.c
+++ b/CommonLibs/trx_vty.c
@@ -466,7 +466,6 @@
 	int rc;
 	struct ctr_threshold ctr;
 
-	struct trx_ctx *trx = trx_from_vty(vty);
 	rc = vty_ctr_name_2_id(argv[0]);
 	if (rc < 0) {
 		vty_out(vty, "No valid ctr_name found for ctr-error-threshold %s%s",
@@ -498,7 +497,6 @@
 	int rc;
 	struct ctr_threshold ctr;
 
-	struct trx_ctx *trx = trx_from_vty(vty);
 	rc = vty_ctr_name_2_id(argv[0]);
 	if (rc < 0) {
 		vty_out(vty, "No valid ctr_name found for ctr-error-threshold %s%s",