[flang] Fix bogus errors from SIZE/SHAPE/UBOUND on assumed-shape

While it is indeed an error to use SIZE, SHAPE, or UBOUND on an
assumed-shape dummy argument without also supplying a DIM= argument
to the intrinsic function, it is *not* an error to use these intrinsic
functions on sections or expressions of such arrays.  Refine the test
used for the error message.

Differential Revision: https://reviews.llvm.org/D128391