Testsuite: remove unused variables

Missing from earlier commit, which removed the only use of those two
variables.

gcc/testsuite/ChangeLog:

	* gfortran.dg/coarray/caf.exp: Remove unused variable.
	* gfortran.dg/dg.exp: Remove unused variable.

gcc/testsuite/gfortran.dg/coarray/caf.exp

@@ -80,7 +80,6 @@ if [check_effective_target_libatomic_available] {
 	    set maybe_atomic_lib "[atomic_link_flags [get_multilibs]]"
 	}
     }
-    set t [get_multilibs]
 }
 
 # Main loop.

gcc/testsuite/gfortran.dg/dg.exp

@@ -67,7 +67,6 @@ if [check_effective_target_libatomic_available] {
     } else {
         set maybe_atomic_lib ""
     }
-  set t [get_multilibs]
 }
 
 set all_flags $DEFAULT_FFLAGS