[WebAssembly] Remove catch_all from AsmParser

Summary:
`catch_all` is from the first version of EH proposal and now has been
removed. There were no tests covering this, and thus no tests to remove
or fix.

Reviewers: aardappel

Subscribers: dschuff, sbc100, jgravelle-google, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63737

llvm-svn: 364360