[release/v1.29.x-0.50bx] Prepare release 1.29.0/0.50b0 (#4349)

* Prepare release 1.29.0/0.50b0

* Update CONTRIB_REPO_SHA to opentelemetrybot/prepare-release-1.29.0-0.50b0

* Update CONTRIB_REPO_SHA for misc too

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Co-authored-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>

[release/v1.29.x-0.50bx] Prepare release 1.29.0/0.50b0 (#4349)

* Prepare release 1.29.0/0.50b0

* Update CONTRIB_REPO_SHA to opentelemetrybot/prepare-release-1.29.0-0.50b0

* Update CONTRIB_REPO_SHA for misc too

---------

Co-authored-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>

[release/v1.28.x-0.49bx] Prepare release 1.28.2/0.49b2 (#4290)

* Prepare release 1.28.2/0.49b2

* Update CONTRIB_REPO_SHA to point to contrib release branch

* Update date to today Nov 18

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Co-authored-by: Aaron Abbott <aaronabbott@google.com>

[release/v1.28.x-0.49bx] Prepare release 1.28.1/0.49b1 (#4262)

Update .readthedocs.yml

Skip testpypi

Skip test pypi

[release/v1.25.x-0.46bx] Prepare release 1.25.0/0.46b0 (#3942)

[release/v1.24.x-0.45bx] Prepare release 1.24.0/0.45b0 (#3819)

Update release.yml