Revert "go: Define a bytePool for TRichTransport"

[fishy]

This reverts commit 344498b.

In our extreme case this actually made things worse. On 30s cpu profiles, although mallocgc reduced from 27.13s to 26.30s, the byte pool itself costed 11.9s. Looking at writeByte and readByte, writeByte increased from 3.69s to 5.89s, and readByte increased from 11.36s to 16.09s.

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[dcelasun]

That's a surprisingly large increase. Unfortunate :(