Bugfix: typo in TXTFMT range check

[pressler-vsc]

Description

This field contains a valid three-character code indicating the format or type of text data.
Note: Valid codes are MTF to indicate USMTF (Refer to STANAG 5500 (NSIF) or MIL-STD-6040
(NITF) for examples of the USMTF format), STA to indicate BCS formatting, UT1 to indicate ECS text
formatting, and U8S to indicate U8S text formatting. Refer to Section 5.17.1 for additional discussion of
standards and the BCS.
Allowed Values: MTF, STA, UT1, U8S