Remove deprecated net-snmp 5.7.3 patch

patches/net-snmp-5.7.3.patch

---- net-snmp-5.7.3/configure	2019-01-19 09:26:17.130519220 +0100
-+++ net-snmp-5.7.3/configure	2019-01-19 09:30:35.517968337 +0100
-@@ -5223,7 +5223,7 @@
- if test "x$ac_cv_user_prompt_NETSNMP_LOGFILE" = "x" -o "x$ac_cv_user_prompt_NETSNMP_SYS_LOC" = "x" -o "x$ac_cv_user_prompt_NETSNMP_SYS_CONTACT" = "x" -o "x$ac_cv_user_prompt_NETSNMP_DEFAULT_SNMP_VERSION" = "x"; then
- { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to prompt for values" >&5
- $as_echo_n "checking whether to prompt for values... " >&6; }
--if ${ac_cv_have_warned+:} false; then :
-+if ${ac_cv_have_warned+:} true; then :
-   $as_echo_n "(cached) " >&6
- else
-