dotfiles: replace default "ubuntu" with proper user after copying

```
$ grep -rnwi "ubuntu" dots/
dots/.config/codeblocks/default.conf:455:                                               <![CDATA[/home/ubuntu/Documents]]>
dots/.config/codeblocks/default.conf:1666:                                      <![CDATA[ubuntu]]>
dots/.config/codeblocks/codesnippets.ini:2:SnippetFile=/home/ubuntu/.config/codeblocks/codesnippets.xml
```