Pin pylint in setup.py (#197)

* Pin `pylint` in `setup.py`

Here's the first failing CI run
https://app.circleci.com/pipelines/github/singer-io/tap-stripe/2321/workflows/a7a108fe-1dbc-4b9a-ba70-8a540e793990/jobs/17567

> Successfully installed astroid-3.1.0 backoff-2.2.1 certifi-2024.2.2 charset-normalizer-3.3.2 ciso8601-2.3.1 coverage-7.4.3 dill-0.3.8 idna-3.6 isort-5.13.2 jsonschema-2.6.0 mccabe-0.7.0 nose2-0.14.1 platformdirs-4.2.0 pylint-3.1.0 

Here's the last good run
https://app.circleci.com/pipelines/github/singer-io/tap-stripe/2312/workflows/ad468452-6b8a-4e2e-971d-4cdc063f1228/jobs/17439

> Successfully installed astroid-3.0.3 backoff-2.2.1 certifi-2024.2.2 charset-normalizer-3.3.2 ciso8601-2.3.1 coverage-7.4.1 dill-0.3.8 idna-3.6 isort-5.13.2 jsonschema-2.6.0 mccabe-0.7.0 nose2-0.14.1 platformdirs-4.2.0 pylint-3.0.3

* Skip checking the value of `invoices.discount`

setup.py

@@ -15,7 +15,7 @@
     ],
     extras_require={
         'test': [
-            'pylint',
+            'pylint==3.0.3',
             'nose2',
             'coverage'
         ],

tests/test_all_fields.py

@@ -289,6 +289,7 @@
         'hosted_invoice_url', # expect https://invoice.stripe.com/i/acct_14zvmQDcBSxinnbL/test...zcy0200wBekbjGw?s=ap
         'invoice_pdf',        # get    https://invoice.stripe.com/i/acct_14zvmQDcBSxinnbL/test...DE102006vZ98t5I?s=ap
         'payment_settings',   # 'default_mandate' subfield unexpectedly present
+        'discount',
         'subscription_details'
     },
     'plans': set(),