modem: new firmware is needed for SHIFTphone 8.1

Please pull the latest firmware from TheMuppets to enable network functionality for SP8.1.

The new firmware works on SP8.0 and SP8.1, however the new firmware is required to enable any functionality for SP8.1.

• https://github.com/TheMuppets/proprietary_vendor_shift_otter/commit/51b77d3d0153ab4c750b8474953d5b4d27f52cfd