[WebAssembly] Move call_indirect_alloca to call.ll

Not sure the distinction between `call.ll` and `call-indirect.ll`,
because `call.ll` also seems to contain many `call_indirect` tests. Also
before D147033 `call-indirect.ll` only contained a single test and it
also tests it with `obj2yaml`, so I guess that file was created for
testing functionalities for object files as well.

We can probably merge these two someday. But anyway, this moves
`call_indirect_alloca` I added in D147033 to `call.ll`, given that that
file contains more `call_indirect` tests and I'm planning to add more
`call_indirect` tests in a followup CL.

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D147396