doc: revise "Breaking Changes and Deprecations"
Revise the "Breaking Changes and Deprecations" section of the Collaborator Guide. Simplify the text. Remove redundant text. The "Deprecations" section is thorough and linked to from this section.
Checklist
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
documentation is changed or added -
commit message follows commit guidelines