Update icon url

Author: LazaroOnline

build/nuspec/GitVersion.Portable.nuspec

@@ -9,7 +9,7 @@
     <copyright>Copyright GitTools 2021.</copyright>
     <licenseUrl>http://www.opensource.org/licenses/mit-license.php</licenseUrl>
     <projectUrl>https://github.com/GitTools/GitVersion</projectUrl>
-    <iconUrl>https://raw.githubusercontent.com/GitTools/graphics/master/GitVersion/icon_100x100.png</iconUrl>
+    <iconUrl>https://raw.githubusercontent.com/GitTools/graphics/master/GitVersion/Color/icon_100x100.png</iconUrl>
     <requireLicenseAcceptance>false</requireLicenseAcceptance>
     <description>Derives SemVer information from a repository following GitFlow or GitHubFlow.</description>
     <tags>Git Versioning GitVersion GitFlowVersion GitFlow GitHubFlow SemVer</tags>