You can remove the VRF temporarily:
sh ip vrf detail | i Id
Only reason this VLAN is even created is because either your VPN-CAM is turned off or you have more than 512 VRFs. If you don't have 512 VRFs, you can free up this internal VLAN without removing VRF by making sure VPN-CAM is activated. This may not be the simplest task as there are various reasons which mean VPN-CAM is disabled, most common reasons are:
- You use 'class-default' in QoS, match 'any any' ACL instead
- You use egress ACL in VRF, remove them
Once there are no reason to disable VPN-CAM, it gets renabled, and those VRF VLANs will disappear. This will also double your VRF performance, as you won't need to recirculate the packet in the PFC.
Without VPN-CAM your first PFC lookup will resolve VRF, second will resolve egress rewrite. With VPN-CAM before packet even hits PFC, VPN-CAM has already told you which table to look against, so PFC will directly return egress rewrite on single lookup.
To confirm if VPN-CAM is used or not, you can issue this command:
remote command switch sh mls vpn-cam 0 511
Long term, maybe change the allocation order, to order from 4k downwards, instead of 1k upwards.