[SemanticConventions] Make project packable (open-telemetry#2683)

Author: Kielek

src/OpenTelemetry.SemanticConventions/OpenTelemetry.SemanticConventions.csproj

@@ -5,7 +5,6 @@
     <Description>OpenTelemetry Semantic Conventions.</Description>
     <PackageTags>$(PackageTags);semantic-conventions</PackageTags>
     <MinVerTagPrefix>SemanticConventions-</MinVerTagPrefix>
-    <IsPackable>false</IsPackable>
   </PropertyGroup>
 
   <!-- Do not run Package Baseline Validation as this package has never released a stable version.