Remove dendrol dependency

[andrewgin]

============================== warnings summary ===============================
make_observations.py:73
  D:\a\stix_patterns\stix_patterns\make_observations.py:73: DeprecationWarning: invalid escape sequence '\s'
    EqualityComparisonExpression(ObjectPath("win-registry-key", ["key"]), "hkey_local_machine\system\bar\foo"))

C:\Users\runneradmin\.virtualenvs\stix_patterns-e-6dQa2b\Lib\site-packages\antlr4\Lexer.py:12
  C:\Users\runneradmin\.virtualenvs\stix_patterns-e-6dQa2b\Lib\site-packages\antlr4\Lexer.py:12: DeprecationWarning: typing.io is deprecated, import directly from typing instead. typing.io will be removed in Python 3.12.
    from typing.io import TextIO

C:\Users\runneradmin\.virtualenvs\stix_patterns-e-6dQa2b\Lib\site-packages\antlr4\Parser.py:6
  C:\Users\runneradmin\.virtualenvs\stix_patterns-e-6dQa2b\Lib\site-packages\antlr4\Parser.py:6: DeprecationWarning: typing.io is deprecated, import directly from typing instead. typing.io will be removed in Python 3.12.
    from typing.io import TextIO

C:\Users\runneradmin\.virtualenvs\stix_patterns-e-6dQa2b\Lib\site-packages\dendrol\lang\STIXPatternParser.py:5
  C:\Users\runneradmin\.virtualenvs\stix_patterns-e-6dQa2b\Lib\site-packages\dendrol\lang\STIXPatternParser.py:5: DeprecationWarning: typing.io is deprecated, import directly from typing instead. typing.io will be removed in Python 3.12.
    from typing.io import TextIO

C:\Users\runneradmin\.virtualenvs\stix_patterns-e-6dQa2b\Lib\site-packages\dendrol\lang\STIXPatternLexer.py:4
  C:\Users\runneradmin\.virtualenvs\stix_patterns-e-6dQa2b\Lib\site-packages\dendrol\lang\STIXPatternLexer.py:4: DeprecationWarning: typing.io is deprecated, import directly from typing instead. typing.io will be removed in Python 3.12.
    from typing.io import TextIO