[chore] Removed frozendict dependency.

It's no longer in use in the codebase.

platypush/install/requirements/alpine.txt

@@ -4,7 +4,6 @@ py3-alembic
 py3-dateutil
 py3-docutils
 py3-flask
-py3-frozendict
 py3-greenlet
 py3-magic
 py3-mypy-extensions

platypush/install/requirements/arch.txt

@@ -4,7 +4,6 @@ python-croniter
 python-dateutil
 python-docutils
 python-flask
-python-frozendict
 python-magic
 python-marshmallow
 python-pip

platypush/install/requirements/debian.txt

@@ -5,7 +5,6 @@ python3-croniter
 python3-dateutil
 python3-docutils
 python3-flask
-python3-frozendict
 python3-greenlet
 python3-magic
 python3-marshmallow

platypush/install/requirements/fedora.txt

@@ -5,7 +5,6 @@ python-croniter
 python-dateutil
 python-docutils
 python-flask
-python-frozendict
 python-greenlet
 python-magic
 python-marshmallow

requirements.txt

@@ -6,7 +6,6 @@ alembic
 croniter
 docutils
 flask
-frozendict
 marshmallow
 marshmallow_dataclass
 paho-mqtt

setup.py

@@ -108,7 +108,6 @@ setup(
         'croniter',
         'docutils',
         'flask',
-        'frozendict',
         'marshmallow',
         'marshmallow_dataclass',
         'psutil',