Tests for locking and unlocking issue comments

[manchicken]

• Adds tests for DELETE /repos/{owner}/{repo}/issues/{issue_number}/lock
• Adds tests for PUT /repos/{owner}/{repo}/issues/{issue_number}/lock

[manchicken]

Fun exercise: test coverage with cargo tarpaulin

|| Tested/Total Lines:
|| src/api/actions/self_hosted_runners.rs: 19/31
|| src/api/actions.rs: 56/189
|| src/api/activity/notifications.rs: 0/67
|| src/api/activity.rs: 0/3
|| src/api/apps/installations.rs: 10/13
|| src/api/apps.rs: 6/20
|| src/api/checks.rs: 0/90
|| src/api/commits/associated_check_runs.rs: 8/14
|| src/api/commits/associated_pull_requests.rs: 1/17
|| src/api/commits/compare_commit.rs: 1/14
|| src/api/commits/create_comment.rs: 10/16
|| src/api/commits.rs: 9/15
|| src/api/current.rs: 8/106
|| src/api/events.rs: 16/31
|| src/api/gists/list_commits.rs: 0/10
|| src/api/gists/list_forks.rs: 0/10
|| src/api/gists/list_gists.rs: 0/27
|| src/api/gists.rs: 0/101
|| src/api/gitignore.rs: 0/13
|| src/api/issues/create.rs: 13/18
|| src/api/issues/list.rs: 36/41
|| src/api/issues/list_labels.rs: 0/25
|| src/api/issues/update.rs: 22/28
|| src/api/issues.rs: 52/276
|| src/api/licenses.rs: 0/7
|| src/api/markdown.rs: 10/26
|| src/api/orgs/events.rs: 0/34
|| src/api/orgs/list_members.rs: 4/10
|| src/api/orgs/list_repos.rs: 0/19
|| src/api/orgs/secrets.rs: 23/37
|| src/api/orgs.rs: 5/32
|| src/api/projects/projects.rs: 69/92
|| src/api/projects.rs: 19/19
|| src/api/pulls/comment.rs: 16/24
|| src/api/pulls/create.rs: 13/18
|| src/api/pulls/list.rs: 22/27
|| src/api/pulls/merge.rs: 13/19
|| src/api/pulls/update.rs: 14/23
|| src/api/pulls.rs: 11/144
|| src/api/ratelimit.rs: 0/3
|| src/api/repos/branches.rs: 0/15
|| src/api/repos/collaborators.rs: 0/12
|| src/api/repos/commits.rs: 0/30
|| src/api/repos/contributors.rs: 9/15
|| src/api/repos/events.rs: 21/36
|| src/api/repos/file.rs: 20/60
|| src/api/repos/forks.rs: 0/28
|| src/api/repos/generate.rs: 0/26
|| src/api/repos/merges.rs: 0/11
|| src/api/repos/pulls.rs: 0/13
|| src/api/repos/releases.rs: 0/108
|| src/api/repos/secrets.rs: 27/42
|| src/api/repos/stargazers.rs: 14/17
|| src/api/repos/status.rs: 0/35
|| src/api/repos/tags.rs: 0/12
|| src/api/repos/teams.rs: 0/12
|| src/api/repos.rs: 27/143
|| src/api/search.rs: 0/28
|| src/api/teams/children.rs: 0/12
|| src/api/teams/create.rs: 0/19
|| src/api/teams/edit.rs: 0/15
|| src/api/teams/invitations.rs: 6/12
|| src/api/teams/list.rs: 0/10
|| src/api/teams/members.rs: 6/12
|| src/api/teams/team_repos.rs: 25/43
|| src/api/teams.rs: 16/30
|| src/api/users/user_repos.rs: 19/19
|| src/api/users.rs: 3/3
|| src/api/workflows.rs: 13/76
|| src/auth.rs: 0/42
|| src/error.rs: 0/11
|| src/etag.rs: 41/54
|| src/from_response.rs: 6/7
|| src/lib.rs: 249/467
|| src/models/date_serde.rs: 12/19
|| src/models/events.rs: 32/39
|| src/models/pulls.rs: 15/15
|| src/models/repos.rs: 0/17
|| src/models/webhook_events.rs: 27/89
|| src/models.rs: 21/29
|| src/page.rs: 51/94
|| src/params.rs: 13/34
|| src/service/body.rs: 5/5
|| src/service/middleware/base_uri.rs: 19/26
|| src/service/middleware/extra_headers.rs: 8/8
|| src/service/middleware/retry.rs: 17/25
||
33.71% coverage, 1208/3584 lines covered

This is after these changes.

[XAMPPRocky]

Thank you for your PR!