fix: incorrect xml foramt

[ChandimaFernando]

Adding a comment at the beginning of .xacro files resulted in the following error:

Captured stderr output: XML parsing error: XML or text declaration not at start of entity: line 2, column 0
when processing file: /workspaces/erobs/install/ur3e_hande_robot_description/share/ur3e_hande_robot_description/urdf/ur_with_hande.xacro

Check that:

• Your XML is well-formed
• You have the xacro xmlns declaration: xmlns:xacro="http://www.ros.org/wiki/xacro"

Fix: The added comment was moved to line 3.
Other fixes: The description file name was corrected from "ur_with_hande.urdf.xacro" to "ur_with_hande.xacro" in relevant Dockerfiles.