Don't solve constraints before ambiguity

It doesn't achieve anything useful, and can be confusing because it
means behaviour is different for names where ambiguity is pruned by type
vs names where it isn't.

src/TTImp/Elab/Ambiguity.idr

@@ -351,8 +351,7 @@ checkAlternative rig elabinfo nest env fc uniq alts mexpected
                                       _ => InTerm False
                 delayOnFailure fc rig env expected ambiguous $
                      \delayed =>
-                       do solveConstraints solvemode Normal
-                          defs <- get Ctxt
+                       do defs <- get Ctxt
                           exp <- getTerm expected
 
                           -- We can't just use the old NF on the second attempt,