[fix][doc] Update docs for Partition increase command

[Apurva007]

Fixes apache#17878

Motivation

The Pulsar documentation currently states that partition update works only for non-global topics. This statement seems to be incorrect as per the below PR:
apache#5306

Modifications

Updated the code comments as well as modified the API documentation for the swagger generation.

Verifying this change

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This change is a trivial rework / code cleanup without any test coverage.

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• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
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• Anything that affects deployment

Documentation

• doc
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• doc-complete

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Flag	Coverage Δ
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systests	24.93% <0.00%> (?)
unittests	72.14% <0.00%> (?)

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