Remove TEXTDOMAIN redefinition from tcar functions.
    
    - Previously, tcar functions redefine TEXTDOMAIN environment variable
      in order to use tcar.po file. This was required in order to reset
      the value set by modules, which were using their own po file. Now,
      both modules and tcar function use the same po file so there is no
      need to redefine TEXTDOMAIN environment variable inside tcar
      functions. So, this update removes TEXTDOMAIN redefinition from tcar
      functions.