@octokit/rest deprecation warnings

- Extension version: 0.12.0

Some new warnings for deprecations that we need to address:

Deprecation: [@octokit/rest] "number" parameter is deprecated for ".pulls.get()". Use "pull_number" instead

Deprecation: [@octokit/rest] octokit.search.issues() has been renamed to octokit.search.issuesAndPullRequests() (2018-12-27)