source-highlight: remove

I don't think this is working and nobody seems to miss it:

```
buczek@theinternet:~$ /usr/bin/source-highlight
/usr/bin/source-highlight: error while loading shared libraries: libboost_regex.so.1.57.0: cannot open shared object file: No such file or directory
buczek@theinternet:~$ ldd /usr/bin/source-highlight
Inconsistency detected by ld.so: dl-version.c: 224: _dl_check_map_versions: Assertion `needed != ((void *)0)' failed!
buczek@theinternet:~$ ldd /usr/lib/libsource-highlight.so.4.0.1
	linux-vdso.so.1 (0x00007ffe1915d000)
	libboost_regex.so.1.57.0 => not found
	libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x00007f894c4ff000)
	libm.so.6 => /lib/libm.so.6 (0x00007f894c1fd000)
	libc.so.6 => /lib/libc.so.6 (0x00007f894be52000)
	libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x00007f894bc3c000)
	/lib64/ld-linux-x86-64.so.2 (0x0000564dec430000)
```