Remove %clean section

None of currently supported distributions need that.
Last one was EL5 which is EOL for a while.

Signed-off-by: Igor Gnatenko <ignatenkobrain@fedoraproject.org>

texstudio.spec

@@ -95,9 +95,6 @@ rm -rf $RPM_BUILD_ROOT%{_datadir}/%{name}/qt_*.qm
 mkdir -p $RPM_BUILD_ROOT%{_datadir}/applications/
 desktop-file-install --dir %{buildroot}%{_datadir}/applications %{SOURCE1}
 
-%clean
-rm -rf $RPM_BUILD_ROOT
-
 %files -f %{name}.lang
 %defattr(-,root,root,-)
 %{_bindir}/texstudio