Correct docstring contradicting class signature

[mdvthu]

Default parameters contradicted docstring

What does this PR do?

• This PR fixes a typo or improves the docs

Current behaviour:

ipython3
import keras_cv
keras_cv.models.StableDiffusionV2?

Init signature:
keras_cv.models.StableDiffusionV2(
    img_height=512,
    img_width=512,
    jit_compile=True,
)
Docstring:     
Keras implementation of Stable Diffusion v2.
...
    jit_compile: bool, whether to compile the underlying models to XLA.
        This can lead to a significant speedup on some systems. Defaults to
        False.

The current function signature contradicts the docstring. This has been fixed with this PR.