remove dependency on spring-cloud-build. (#1933)

Author: rghetia

contrib/spring/build.gradle

@@ -13,7 +13,6 @@ dependencies {
             project(':opencensus-contrib-http-servlet'),
             libraries.spring_aspects,
             libraries.spring_context,
-            libraries.spring_cloud_build,
             libraries.findbugs_annotations,
             libraries.spring_boot_starter_web2,
             libraries.httpcomponents