x/tools/gopls: errors when navigating through `git` ir `gitlens` URIs do not disappear anymore

[inliquid]

1. VS Code
2. gopls@master

Previously these errors would disappear after git or gitlens tab was closed. Now they stay until language server restart.

[gopherbot]

Thank you for filing a gopls issue! Please take a look at the Troubleshooting guide, and make sure that you have provided all of the relevant information here.

[stamblerre]

This is a result of CL 208237, which removed the previous behavior of clearing diagnostics when a file was closed. This change was made because gopls now shows diagnostics for an entire workspace. I think the right approach here will be for us to handle these files correctly (without showing errors). As a result, I will close this issue in favor of #33699.