Fix CI.

[peterhuene]

This PR fixes CI as currently Wasmtime will panic if non-funcref tables are
used (not currently implemented).

[peterhuene]

This appears to have been was regressed by bytecodealliance/wasmtime#1524.

Previously we were just cloning an internal table type in Table::ty and now we're calling TableType::from_wasmtime_table which panics if the element type is not funcref.

@sunfishcode previously the C API was able to describe anyref table imports and exports, but now we hit the assertion in TableType::from_wasmtime_table. Given that anyref tables aren't really implemented yet in Wasmtime, how should we fix this? Should the .NET tests simply just stick to funcref tables in the test modules until Wasmtime reference types implementation is more complete or should we relax the assertion such that anyref is valid?

Wasmtime will unimplemented! panic with the following module despite reference types being enabled:

(module
  (table $t 1 anyref)
)

[peterhuene]

I'm going to merge this for now and we can revisit when more of the reference types proposal is implemented.