Change an rviz_ogre_vendor dependency to libfreetype-dev. (#1167)

The situation is complicated, but in versions of Ubuntu
prior to Focal and versions of Debian prior to Bookworm,
the name of the library was 'libfreetype6-dev'.  Since
Focal and Bookworm, the name of the library is 'libfreetype-dev'.
While 'libfreetype-dev' provides a "virtual package"
for 'libfreetype6-dev', we should really use the new canonical
name.

Further, there is currently a bug on ros_buildfarm where
it doesn't properly deal with "virtual packages" like this.
This is currently preventing this package from building on
Ubuntu Noble.  That bug is being worked on separately.

Finally, I'll note that we already have a libfreetype-dev
key in rosdep, so we just switch to using that here which
should work around the bug on the buildfarm, and also use
the correct canonical name going forward.

Signed-off-by: Chris Lalancette <clalancette@gmail.com>

rviz_ogre_vendor/package.xml

@@ -23,8 +23,8 @@
   <buildtool_depend>ament_cmake</buildtool_depend>
   <buildtool_depend>ament_cmake_vendor_package</buildtool_depend>
 
-  <build_depend>libfreetype6-dev</build_depend>
-  <build_export_depend>libfreetype6-dev</build_export_depend>
+  <build_depend>libfreetype-dev</build_depend>
+  <build_export_depend>libfreetype-dev</build_export_depend>
   <exec_depend>libfreetype6</exec_depend>
 
   <depend>libx11-dev</depend>