Go back to one requirements.txt, simplify workflow

The workflow can now use .pylintrc and the pylint req in
requirements.txt rather than having the options inline and installing it
separately

.github/workflows/pylint.yml

@@ -21,8 +21,7 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         pip install -r requirements.txt
-        pip install pylint
     - name: Analysing the code with pylint
       run: |
-        pylint bookwyrm/ --ignore=migrations --disable=E1101,E1135,E1136,R0903,R0901,R0902,W0707,W0511,W0406,R0401,R0801
+        pylint bookwyrm/