[flang] Pad output correctly after tabbing with ADVANCE='no' (bug#63111)

Correct the code that implements the production of spaces to bring the
furthestPositionInRecord up to a positionInRecord that was tabbed forward
by a T or TR control edit descriptor.

Fixes bug https://github.com/llvm/llvm-project/issues/63111.

Differential Revision: https://reviews.llvm.org/D152201