[Instrumentation.ConfluentKafka] Remove ImplicitUsings property (open-telemetry#2179)

Co-authored-by: joegoldman2 <[email protected]>

Author: joegoldman2

src/OpenTelemetry.Instrumentation.ConfluentKafka/OpenTelemetry.Instrumentation.ConfluentKafka.csproj

@@ -7,7 +7,6 @@
     <PackageTags>$(PackageTags);distributed-tracing;Kafka;Confluent.Kafka</PackageTags>
     <IncludeSharedExceptionExtensionsSource>true</IncludeSharedExceptionExtensionsSource>
     <MinVerTagPrefix>Instrumentation.ConfluentKafka-</MinVerTagPrefix>
-    <ImplicitUsings>true</ImplicitUsings>
   </PropertyGroup>
 
   <!-- Do not run Package Baseline Validation as this package has never released a stable version.