Remove redundant null-forgiving operator in MamJsonParser.ReadClassRewrites

[Copilot]

MamJsonParser.ReadClassRewrites used the ! null-forgiving operator on classRewrite, which is already proven non-null by the if (classRewrite == null) continue; guard immediately above. This violates the repo rule against using ! and is redundant—the sibling ReadGlobalMethodCalls makes the identical call without it.

Changes

• Drop the ! from the TryReadClassFromTo call in ReadClassRewrites:

- if (!TryReadClassFromTo (classRewrite!, out var from, out var to)) {
+ if (!TryReadClassFromTo (classRewrite, out var from, out var to)) {

No other lines changed. The out-of-scope JsonNode.Parse ("{}")! in ReadJson was left untouched.