Fixing desired capabilities and find element deprecation

[MrTeale]

This PR closes #1870

When running the tests, DeprecationWarning: desired_capabilities has been deprecated, please pass in a Service object is shown.

There was also another similar message that has been dealt with in this PR: DeprecationWarning: find_element_by_* commands are deprecated. Please use find_element() instead. This has been solved by find_element and find_elements now taking an attribute keyword, as a string, for the type of selector that is being used. default is set to CSS_SELECTOR as that's what historically find_element was solely for.

Contributor Checklist

• I have broken down my PR scope into the following TODO tasks
  • Fix desired_capabilities deprecation warning
  • Fix find_element_by_* deprecation warning
• I have run the tests locally and they passed. (refer to testing section in contributing)
• I have added entry in the CHANGELOG.md

[MrTeale]

This is currently causing some tests to be flaky. Looking into why a bit more so until then, PLEASE DO NOT MERGE.

If you have any questions or feedback, let me know.

[alexcjohnson]

💃 Looks great, thanks for the contribution @MrTeale

The table-server-test failure here is nothing to do with your changes, it's an intermittent failure we've seen recently, so far we haven't figured out the origin but it shouldn't block your PR.

(approved pending the two comments above plus a changelog entry as you noted)

[MrTeale]

Thanks @alexcjohnson! This should be ready to go now