Revert "deps(build): update esbuild-loader to 4.3.0 (#6622)" (#6660)

This reverts commit 8d2d335.

## Problem
Upgrading esbuild-loader broke loading mynah-ui

## Solution
Revert for now

---

- Treat all work as PUBLIC. Private `feature/x` branches will not be
squash-merged at release time.
- Your code changes must meet the guidelines in
[CONTRIBUTING.md](https://github.com/aws/aws-toolkit-vscode/blob/master/CONTRIBUTING.md#guidelines).
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Apache 2.0 license.

Author: jpinkney-aws