CLEANUP: vars: Remove void vars_unset_by_name(const char*, size_t, struct sample*)

With "MINOR: lua: Use vars_unset_by_name_ifexist()" the last user was
removed and as outlined in that commit there is no good reason for this
function to exist.

May be backported together with the commit mentioned above.
diff --git a/include/proto/vars.h b/include/proto/vars.h
index 6152f5c..caf00ff 100644
--- a/include/proto/vars.h
+++ b/include/proto/vars.h
@@ -10,7 +10,6 @@
 void vars_set_by_name_ifexist(const char *name, size_t len, struct sample *smp);
 void vars_set_by_name(const char *name, size_t len, struct sample *smp);
 void vars_unset_by_name_ifexist(const char *name, size_t len, struct sample *smp);
-void vars_unset_by_name(const char *name, size_t len, struct sample *smp);
 int vars_get_by_desc(const struct var_desc *var_desc, struct sample *smp);
 int vars_check_arg(struct arg *arg, char **err);
 
diff --git a/src/vars.c b/src/vars.c
index a6807fa..08b1307 100644
--- a/src/vars.c
+++ b/src/vars.c
@@ -584,21 +584,6 @@
 }
 
 
-/* This function unset a variable.
- * In error case, it fails silently.
- */
-void vars_unset_by_name(const char *name, size_t len, struct sample *smp)
-{
-	enum vars_scope scope;
-
-	/* Resolve name and scope. */
-	name = register_name(name, len, &scope, 1, NULL);
-	if (!name)
-		return;
-
-	sample_clear_stream(name, scope, smp);
-}
-
 /* this function fills a sample with the
  * variable content. Returns 1 if the sample
  * is filled, otherwise it returns 0.