Remove 'gfortran.dg/goacc/loop-6.f95'

What it's testing is adequately covered in other
'gfortran.dg/goacc/loop-2-parallel-*.f95' testcases.

	gcc/testsuite/
	* gfortran.dg/goacc/loop-6.f95: Remove.

gcc/testsuite/gfortran.dg/goacc/loop-6.f95

-program test
-  implicit none
-  integer :: i, j
-
-  !$acc parallel
-    !$acc loop auto
-    DO i = 1,10
-    ENDDO
-    !$acc loop gang
-    DO i = 1,10
-    ENDDO
-    !$acc loop gang(static:5)
-    DO i = 1,10
-    ENDDO
-    !$acc loop gang(static:*)
-    DO i = 1,10
-    ENDDO
-    !$acc loop gang
-    DO i = 1,10
-      !$acc loop vector
-      DO j = 1,10
-      ENDDO
-      !$acc loop worker
-      DO j = 1,10
-      ENDDO
-    ENDDO
-
-    !$acc loop worker
-    DO i = 1,10
-    ENDDO
-    !$acc loop worker
-    DO i = 1,10
-      !$acc loop vector
-      DO j = 1,10
-      ENDDO
-    ENDDO
-    !$acc loop gang worker
-    DO i = 1,10
-    ENDDO
-
-    !$acc loop vector
-    DO i = 1,10
-    ENDDO
-    !$acc loop vector(5) ! { dg-error "length arguments" }
-    DO i = 1,10
-    ENDDO
-    !$acc loop vector(length:5) ! { dg-error "length arguments" }
-    DO i = 1,10
-    ENDDO
-    !$acc loop vector
-    DO i = 1,10
-    ENDDO
-    !$acc loop gang vector
-    DO i = 1,10
-    ENDDO
-    !$acc loop worker vector
-    DO i = 1,10
-    ENDDO
-
-    !$acc loop auto
-    DO i = 1,10
-    ENDDO
-  !$acc end parallel
-
-  !$acc parallel loop vector
-  DO i = 1,10
-  ENDDO
-  !$acc parallel loop vector(5) ! { dg-error "length arguments" }
-  DO i = 1,10
-  ENDDO
-  !$acc parallel loop vector(length:5) ! { dg-error "length arguments" }
-  DO i = 1,10
-  ENDDO
-end