assembler can't handle %{ %} casm blocks

[quasilyte]

We may want to treat them as comments for now.
Cairo1 compiler still produces inline-hints in some modes.
Treating them as comments looks better than a parse failure.

Here is an example of a casm file that contains {%%} blocks:
https://github.com/starkware-libs/cairo/blob/405b84767f01d6c98a0db3351e89c51b921f3389/tests/test_data/match_or.casm#L92

I'm not sure we're interested in extracting the pythonic hints from this source, but it's also doable.
This issue is just about the inability to use any casm files that contain inline cairo0-style hints inside them in our test suits.