chore(x/tx): partly revert NewEncoder usage

[julienrbrt]

Description

Partly revert #16684. Using the Encode methods adds an unnecessary newline.

This leads to a small diff when marshaling compared to previously https://github.com/cosmos/cosmos-sdk/actions/runs/5524118523/jobs/10075983329

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[tac0turtle]

LGTM, did we use a new encoder for any particular reason before?

[julienrbrt]

LGTM, did we use a new encoder for any particular reason before?

It was to marshal directly to the writer. but we can still do that in two steps without significant perf impact for this case.