Remove System.Net.Http v4.3.0

[anchitj]

For #2054. Remove System.Net.Http v4.3.0

[cla-assistant[bot]]

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:white_check_mark: anchitj
:x: janjwerner-confluent
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[cla-assistant[bot]]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}