Clean up `CHANGELOG.md` taxonomy after PR #560

**Problem description**
PR #560 placed several entries in the wrong Keep-a-Changelog section:

- Under `### Fixed`:
> Expanded the `CustomModule` section in the wiki `Getting-started` page to document the `-Features` parameter, list every supported feature value and show non-interactive examples.

This is a documentation improvement and belongs under `### Changed` (or a dedicated documentation subsection).

- Under `### Added`:
> `New-SampleModule` exposes a `MainGitBranch` parameter (defaults to `main`)

The addition is fine under `### Added`, but the behavioral implication (default `main` vs. historical `master`) needs a parallel `### Changed` entry (tracked separately).

The repo enforces changelog discipline via QA tests, so keeping the categories clean matters.

**Verbose logs**
N/A

**How to reproduce**
Read the `Unreleased` section of `CHANGELOG.md`.

**Expected behavior**
Entries are categorized per Keep a Changelog conventions: bug fixes under `### Fixed`, documentation and non-bug behavior changes under `### Changed`, net-new capabilities under `### Added`.

**Current behavior**
Documentation entry appears under `### Fixed`; default-behavior change is implicit under `### Added` only.

**Suggested solution**
- Move the wiki-update entry from `### Fixed` to `### Changed`.
- Add the missing `### Changed` entries identified in the related `MainGitBranch` and parameter-set follow-up issues.

**Operating system the target node is running**
N/A

**PowerShell version and build the target node is running**
N/A

**Module version used**
Sampler `Unreleased` / post-#560.

Open CHANGELOG.md and inspect the Unreleased section, then review the QA tests that enforce Keep-a-Changelog categories. Move the CustomModule wiki-update entry to Changed and add the documented MainGitBranch and parameter-set follow-up entries; done means documentation is under Changed, capabilities under Added, and the QA checks pass.

Written by the indexing model from the issue text.