utils/getdeveloperlib.py: explicitly set devs document encoding

utils/getdeveloperlib.py: explicitly set devs document encoding

Explicitly indicate the file encoding to UTF-8 for the DEVELOPERS
document. This prevents Unicode decoding errors when printing E-Mail
entries with Unicode characters on systems using an alternative default
encoding (e.g. 'CP1252').

This corrects the following observed error:

    $ ./utils/get-developers outgoing/*
    Traceback (most recent call last):
      File "utils\get-developers", line 105, in <module>
        __main__()
      File "utils\get-developers", line 47, in __main__
        devs = getdeveloperlib.parse_developers()
      File "...\buildroot\utils\getdeveloperlib.py", line 239, in parse_developers
        for line in f:
      File "...\Python<ver>\lib\encodings\cp1252.py", line 23, in decode
        return codecs.charmap_decode(input,self.errors,decoding_table)[0]
    UnicodeDecodeError: 'charmap' codec can't decode byte 0x81 in position 6659: character maps to <undefined>

Signed-off-by: James Knight <james.d.knight@live.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>