Remove quotes from setup.cfg

Push was failing with the message:
```Invalid value for classifiers. Error: Classifiers ['"Intended Audience :: Developers"', '"License :: OSI Approved :: Apache Software License"', '"Topic :: Database :: Front-Ends"'] are not valid classifiers.```
Looking at https://setuptools.pypa.io/en/latest/userguide/declarative_config.html#using-a-src-layout, strings don't need quotes

Author: NiallEgan

cmdexec/clients/python/setup.cfg

@@ -1,18 +1,18 @@
 [metadata]
 name = databricks-sql-connector
 version = attr: databricks.sql.__version__
-description = "Databricks SQL Connector for Python"
+description = Databricks SQL Connector for Python
 long_description = file: README.md
 long_description_content_type = text/markdown
-url = "https://databricks.com"
-author = "Databricks"
-author_email = "feedback@databricks.com"
-license = "http://www.apache.org/licenses/LICENSE-2.0"
+url = https://databricks.com
+author = Databricks
+author_email = feedback@databricks.com
+license = http://www.apache.org/licenses/LICENSE-2.0
 classifiers =
-    "Intended Audience :: Developers"
-    "License :: OSI Approved :: Apache Software License"
-    "Operating System :: OS Independent"
-    "Topic :: Database :: Front-Ends"
+    Intended Audience :: Developers
+    License :: OSI Approved :: Apache Software License
+    Operating System :: OS Independent
+    Topic :: Database :: Front-Ends
 install_requires =
     thrift >= 0.13.0
     pyarrow >= 5.0.0