Modify Modlauncher bytecode provider class parser flags

[Su5eD]

Changes the flags used to read ClassNodes in Mixin's modlauncher bytecode provider class, MixinLaunchPluginLegacy, to use 0 instead of ClassReader.EXPAND_FRAMES. This is to ensure the correctness of local variable analysis, as well as to achieve parity with Fabric's flag usage (which is currently the opposite of modlauncher's settings).

Mixin/src/modlauncher/java/org/spongepowered/asm/launch/MixinLaunchPluginLegacy.java

Line 238 in a209179

classReader.accept(classNode, ClassReader.EXPAND_FRAMES);

For a complete description of the issue, please see neoforged/NeoForge#768.

[modmuss50]

Seems fine to me, I have no way to test this change, so might be best to get another neoforge dev to approve as well?