Remove code 1002 CannotCreateRoom

[jpdillingham]

Closes #821

There are only 2 codes in the 100x region: 1001 CannotConnect, and 1003 CannotJoinRoom.

According to the Nicotine+ docs this code has only been observed being sent when attempting to join/create a private room that already exists.

I'm going to leave this named CannotJoinRoom, which covers both the (hypothetical) join and create scenarios, as you must join a room to create it. And the work is already done and tested.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.19%. Comparing base (8e260ea) to head (15facc4).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #967      +/-   ##
==========================================
+ Coverage   99.16%   99.19%   +0.02%     
==========================================
  Files         189      189              
  Lines        6704     6704              
  Branches     1024     1024              
==========================================
+ Hits         6648     6650       +2     
+ Misses         42       41       -1     
+ Partials       14       13       -1     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.