Remove duplicate API request functions and update docs

[NowinskiK]

This commit removes the Invoke-FabricAPIRequest_duplicate and Invoke-FabricRestMethodExtended functions from the codebase, as they were redundant.

Pull Request

Pull Request (PR) description

Task list

• The PR represents a single logical change. i.e. Cosmetic updates should go in different PRs.
• Added an entry under the Unreleased section of in the CHANGELOG.md as per format.
• Local clean build passes without issue or fail tests (build.ps1 -ResolveDependency -Tasks build, test).
• Comment-based help added/updated.
• Examples appropriately added/updated.
• Unit tests added/updated..
• Integration tests added/updated (where possible).
• Documentation added/updated (where applicable).
• Code follows the contribution guidelines.

[github-actions]

Linux Test Results

3 113 tests   3 098 ✅  1m 31s ⏱️
1 076 suites     15 💤
    1 files        0 ❌

Results for commit 839e6e2.

[github-actions]

WinPS51 Test Results

3 326 tests   3 311 ✅  1m 38s ⏱️
1 077 suites     15 💤
    1 files        0 ❌

Results for commit 839e6e2.

[github-actions]

WinPS71 Test Results

3 326 tests   3 311 ✅  1m 36s ⏱️
1 077 suites     15 💤
    1 files        0 ❌

Results for commit 839e6e2.