readme.md: Removed explicit gem versions
readme.md: Removed explicit gem versions

It feels they aren't needed now that you get the right versions with a plain gem install, and it also makes the readme more easily be outdated if keep them here.

Here are the current versions I got when running `gem install`:

```shell
$ gem install ruby-debug-ide
Fetching: ruby-debug-ide-0.6.1.gem (100%)
Building native extensions. This could take a while...
Successfully installed ruby-debug-ide-0.6.1
Parsing documentation for ruby-debug-ide-0.6.1
Installing ri documentation for ruby-debug-ide-0.6.1
Done installing documentation for ruby-debug-ide after 0 seconds
1 gem installed
$ gem install debase
Building native extensions. This could take a while...
Successfully installed debase-0.2.2
Parsing documentation for debase-0.2.2
Installing ri documentation for debase-0.2.2
Done installing documentation for debase after 0 seconds
1 gem installed
```
rubyide/vscode-ruby,rubyide/vscode-ruby,rubyide/vscode-ruby,rubyide/vscode-ruby,rubyide/vscode-ruby