Remove redundant descriptions from classref

[timothyqiu]

The class reference contains many redundant descriptions, for example:

PackedVector3Array get_backed_up_vectors() const
# Returns X as [Type]. This is literally repeating the return type.
    Returns the cache of up vectors as a PackedVector3Array.
# Suggested:
    Returns the cache of up vectors.

bool get_particle_flag(particle_flag: ParticleFlags) const
# See [Enum] for options. Possible values of the argument can be inferred from its type.
    Returns true if the specified particle flag is enabled. See ParticleFlags for options.
# Suggested:
    Returns true if the specified particle flag is enabled. 

These kind of description are only meaningful when extra information are given. For example:

• The return type does not behave normally. e.g. The returned PackedVector3Array which is a copy of the original data instead of a reference.
• The available options are a subset of the enum. e.g. See the MASK_* constants in SomeEnum for options.