Constrain the CHECK pattern more to prevent it from triggering on incidental inlinings.

The issue is that this test expression can trigger compilation of
dependencies if they're not already in the Dex cache, which in turn
will log their inlining passes.  None of those seem to have for loops,
however.

Author: axch

tests/inline-tests.dx

@@ -103,8 +103,10 @@ def id'(x:Nat) -> Nat = x
       Right k -> 2
   for j:(Fin 3). xs[Left j]
 -- CHECK: === inline ===
+-- CHECK: for
 -- CHECK: case
 -- CHECK: === inline ===
+-- CHECK: for
 -- CHECK-NOT: case
 
 -- CHECK-LABEL: Inlining carries out the case-of-case optimization