[test] Update a couple of crasher signatures

Author: hamishknight

validation-test/IDE/crashers/ASTMangler-mangleDeclAsUSR-8b1e4c.swift renamed to validation-test/IDE/crashers/ASTMangler-mangleDeclWithPrefix-8b1e4c.swift

@@ -1,3 +1,3 @@
-// {"kind":"complete","original":"2201e4ed","signature":"swift::Mangle::ASTMangler::mangleDeclAsUSR(swift::ValueDecl const*, llvm::StringRef)"}
+// {"kind":"complete","original":"2201e4ed","signature":"swift::Mangle::ASTMangler::mangleDeclWithPrefix(swift::ValueDecl const*, llvm::StringRef)"}
 // RUN: not --crash %target-swift-ide-test -code-completion -batch-code-completion -skip-filecheck -code-completion-diagnostics -source-filename %s
 enum a<b{ protocol c{ class d{ class f<b let e=f #^^#