Fix MD026 warnings

The following warnings are generated by using markdownlint analysis:
```
docs/Network-Configuration.md:58:25 MD026/no-trailing-punctuation Trailing punctuation in heading [Punctuation: ':']
```
Refer to markdown-lint [1] to fix MD026
[1]: https://github.com/updownpress/markdown-lint/blob/master/rules/026-no-trailing-punctuation.md

Signed-off-by: George Liu <liuxiwei@ieisystem.com>
Change-Id: I0ceefdccaee128bce0d86228bda819a9482074e2
diff --git a/docs/Network-Configuration.md b/docs/Network-Configuration.md
index fc7b1d9..86362e6 100644
--- a/docs/Network-Configuration.md
+++ b/docs/Network-Configuration.md
@@ -55,7 +55,7 @@
 
 ## UseCases
 
-### Configure IP address:
+### Configure IP address
 
 ```sh
 busctl call xyz.openbmc_project.Network /xyz/openbmc_project/network/<interface>