setup.py: Remove id3c as a requirement

The core id3c package is technically required for id3c-customizations,
but the editable install of id3c through pipenv does not resolve this
dependency. Details can be found in the open issue here:
pypa/pipenv#4235

setup.py

@@ -56,7 +56,7 @@
     python_requires = ">=3.6",
 
     install_requires = [
-        "id3c >=2020.2",
+        # "id3c >=2020.2", ID3C is a required dependency, but this doesn't resolve with pipenv editable installs
         "click >=7.0",
         "regex",
         "requests",