Fix MD025 warnings

The following warnings are generated by using markdownlint analysis:
```
docs/Network-Configuration.md:26 MD025/single-title/single-h1 Multiple top-level headings in the same document [Context: "# DbusObjects"]
docs/Network-Configuration.md:56 MD025/single-title/single-h1 Multiple top-level headings in the same document [Context: "# UseCases"]
```
Refer to markdown-lint [1] to fix MD025
[1]: https://github.com/updownpress/markdown-lint/blob/master/rules/025-single-h1.md

Signed-off-by: George Liu <liuxiwei@ieisystem.com>
Change-Id: I0912159d293b770bf9f5e2b4e398dae344094851
1 file changed