Harmonize ObservationConvention parameters in gRPC support

Such parameters are usually named "customConvention" so this commit
aligns to that naming.

See gh-49730

module/spring-boot-grpc-client/src/main/java/org/springframework/boot/grpc/client/autoconfigure/GrpcClientObservationAutoConfiguration.java

@@ -53,9 +53,9 @@ public final class GrpcClientObservationAutoConfiguration {
 	@GlobalClientInterceptor
 	@ConditionalOnMissingBean
 	ObservationGrpcClientInterceptor grpcClientObservationInterceptor(ObservationRegistry observationRegistry,
-			ObjectProvider<GrpcClientObservationConvention> convention) {
+			ObjectProvider<GrpcClientObservationConvention> customConvention) {
 		ObservationGrpcClientInterceptor interceptor = new ObservationGrpcClientInterceptor(observationRegistry);
-		convention.ifAvailable(interceptor::setCustomConvention);
+		customConvention.ifAvailable(interceptor::setCustomConvention);
 		return interceptor;
 	}
 

module/spring-boot-grpc-server/src/main/java/org/springframework/boot/grpc/server/autoconfigure/GrpcServerObservationAutoConfiguration.java

@@ -58,9 +58,9 @@ public final class GrpcServerObservationAutoConfiguration {
 	@GlobalServerInterceptor
 	@ConditionalOnMissingBean
 	ObservationGrpcServerInterceptor grpcServerObservationInterceptor(ObservationRegistry observationRegistry,
-			ObjectProvider<GrpcServerObservationConvention> convention) {
+			ObjectProvider<GrpcServerObservationConvention> customConvention) {
 		ObservationGrpcServerInterceptor interceptor = new ObservationGrpcServerInterceptor(observationRegistry);
-		convention.ifAvailable(interceptor::setCustomConvention);
+		customConvention.ifAvailable(interceptor::setCustomConvention);
 		return interceptor;
 	}