[StmtProfile] Don't profile the body of lambda expressions

Close https://github.com/llvm/llvm-project/issues/87609

We tried to profile the body of the lambda expressions in
https://reviews.llvm.org/D153957. But as the original comments show,
it is indeed dangerous. After we tried to skip calculating the ODR
hash values recently, we have fall into this trap twice.

So in this patch, I choose to not profile the body of the lambda
expression. The signature of the lambda is still profiled.