fix(deps): update dependency xblock to v5

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
XBlock	4.0.1 -> 5.1.0

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Release Notes

openedx/XBlock (XBlock)

v5.1.0

Compare Source

• added ability to override an XBlock with the 'xblock.v1.overrides' entry point
• added ability to override an XBlock Aside with the 'xblock_asides.v1.overrides' entry point

v5.0.0

Compare Source

• dropped python 3.8 support
• transitioned from deprecated pkg_resources lib to importlib.resources

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