Change in Cisco MIB download place

As stated at [SNMP
FAQ](https://www.cisco.com/c/en/us/support/docs/ip/simple-network-management-protocol-snmp/9226-mibs-9226.html#anc4),
Github is a trusted place to fetch MIBs, so using it.

Dockerfile

@@ -18,10 +18,10 @@ RUN sed -i /etc/apt/sources.list -e 's/$/ non-free'/ && \
 
 # Install required packages and files required for snmp
 RUN mkdir -p /var/lib/mibs/ietf && \
-    curl -s ftp://ftp.cisco.com/pub/mibs/v2/CISCO-SMI.my -o /var/lib/mibs/ietf/CISCO-SMI.txt && \
-    curl -s ftp://ftp.cisco.com/pub/mibs/v2/CISCO-TC.my -o /var/lib/mibs/ietf/CISCO-TC.txt && \
-    curl -s ftp://ftp.cisco.com/pub/mibs/v2/CISCO-VTP-MIB.my -o /var/lib/mibs/ietf/CISCO-VTP-MIB.txt && \
-    curl -s ftp://ftp.cisco.com/pub/mibs/v2/MPLS-VPN-MIB.my -o /var/lib/mibs/ietf/MPLS-VPN-MIB.txt
+    curl -sL https://github.com/cisco/cisco-mibs/raw/main/v2/CISCO-SMI.my -o /var/lib/mibs/ietf/CISCO-SMI.txt && \
+    curl -sL https://github.com/cisco/cisco-mibs/raw/main/v2/CISCO-TC.my -o /var/lib/mibs/ietf/CISCO-TC.txt && \
+    curl -sL https://github.com/cisco/cisco-mibs/raw/main/v2/CISCO-VTP-MIB.my -o /var/lib/mibs/ietf/CISCO-VTP-MIB.txt && \
+    curl -sL https://github.com/cisco/cisco-mibs/raw/main/v2/MPLS-VPN-MIB.my -o /var/lib/mibs/ietf/MPLS-VPN-MIB.txt
 
 # Configure apache and required PHP modules
 RUN docker-php-ext-configure mysqli --with-mysqli=mysqlnd && \