You can use the Diskpart command to delete the Recovery partition and then, of course, use Disk Management to invoke the Extend Volume command to extend your C: partition to encompass the resultant unallocated disk-space.
The basic Diskpart final command you will use after invoking/using Diskpart and selecting the Recovery partition is delete partition override. You should get the message "DiskPart successfully deleted the selected partition."
I don't know if you're familiar with using Diskpart. If you're not, do a Google search - there's plenty of information re using this valuable tool.