[Format] Fix 'auto x(T&&, T &&)->F' with PAS_Left.

Summary:
An heuristic targetting `x && x->foo` was targed overly broadly and caused the
last T&& to be treated as a binary operator.

Reviewers: hokein

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D73334