Check the hidden cap on `firetolerance`

https://github.com/beyond-all-reason/spring/blob/e55ce6231a0b125f41f56688277dca95ddc7b3bd/rts/Sim/Weapons/Weapon.cpp#L371-L372

The first line checks the angle against `maxFireAngle` (which is the internal engine name for what Lua defs call `fireTolerance`).
The second line looks like it checks the same angle against an arbitrary 20° angle.
This sounds like it would mean setting firetolerance above 20° does nothing because any angle larger than 20° is caught anyway by the hardcoded check.

The task is to:
* verify that the description above matches reality
* get rid of the hardcoded check
* I don't see a reason to cap `fireTolerance`, especially since the default is already supposed to match the hardcoded check. But if you discover a good reason the check was there then put an explicit maximum on `fireTolerance` in `WeaponDef.cpp`.

Start at rts/Sim/Weapons/Weapon.cpp lines 371-372 and trace maxFireAngle to confirm whether the hardcoded 20° check overrides Lua fireTolerance values. Then inspect WeaponDef.cpp for the definition and defaults; done means removing the hardcoded check, or documenting and enforcing an explicit maximum if the investigation finds a valid reason for the cap.

Written by the indexing model from the issue text.