Bug - [Page] - [update onPageResize prop default value]

[tlabaj]

Describe the problem
A clear and concise description of the problem. Which components are affected?
Update the default value for onPageResize
How do you reproduce the problem?
Resize observe get created even when there is not sidebar and consumer does not define onPageResize
See issue #7810 for more details

Is this issue blocking you?
List the workaround if there is one.
work around implemented in PR #7811

[andyyvo]

@tlabaj @wise-king-sullyman from reading #7811 are we looking to remove onPageResize: (): void => null, under PageProps on line 104?

[wise-king-sullyman]

@andyyvo yes I think that's correct, removing that default value so that the prop is undefined if it isn't passed.

Though additionally I would check and make sure that doing so doesn't cause any errors before you put the PR up, since it would if there's anywhere that we're relying on that default to be there.