Update prometheus-net.DotNetRuntime.csproj (#24)

Bumping minor version to reflect targeting .net standard 2.1

Author: djluck

src/prometheus-net.DotNetRuntime/prometheus-net.DotNetRuntime.csproj

@@ -14,7 +14,7 @@
         <RootNamespace>Prometheus.DotNetRuntime</RootNamespace>
         <AssemblyName>prometheus-net.DotNetRuntime</AssemblyName>
         <PackageId>prometheus-net.DotNetRuntime</PackageId>
-        <Version>$(PromMajorVersion).2.0</Version>
+        <Version>$(PromMajorVersion).3.0</Version>
         <Authors>James Luck</Authors>
         <PackageTags>Prometheus prometheus-net IOnDemandCollector runtime metrics gc jit threadpool contention stats</PackageTags>
         <PackageProjectUrl>https://github.com/djluck/prometheus-net.DotNetRuntime</PackageProjectUrl>