chore: remove package description from the readme

This removes the description from the package readme. The desciption of the package is
shown on nuget.org in the list view and if no package readme is defined on the detail view of
a package version. Since we provide a package readme we do not need the description shown
twice.

src/semver/package-readme.md

@@ -1,5 +1,3 @@
-SemVer is a .NET library for parsing, comparing, formatting, and serializing semantic versions and version ranges.
-
 ## Features
 
 - **Parsing:** parse semantic version strings into structured objects.