opcode 1I/Q/X is not supported for Beidou

[mikehb]

Describe the bug
As explained by table 19 of https://files.igs.org/pub/data/format/rinex305.pdf, when reading a RINEX 3.02 file, both 1I/Q/X and 2I/Q/X observation codes should be accepted and treated the same as 2I/Q/X in the current RINEX standard. But gnss_lib_py doesn't support this. This will introduce following trace message

Traceback (most recent call last):
  File "/home/mikehuang/programs/./obs_featuring.py", line 20, in <module>
    staNavData = glp.RinexObs(file)
                 ^^^^^^^^^^^^^^^^^^
  File "/home/mikehuang/.local/lib/python3.11/site-packages/gnss_lib_py/parsers/rinex_obs.py", line 106, in __init__
    signal_type = signal_type_dict[constellation][band]
                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
KeyError: '1I'