Revert "Remove Scope.close() method."
Revert "Remove Scope.close() method."

This reverts commit 969f95088a3a1e490460ad53931b24e46e6ca907.

The close() override is necessary to suppress a deprecation warning from
NonThrowingCloseable.close().

bogdandrutu/instrumentation-java,sebright/opencensus-java,songy23/instrumentation-java,sebright/opencensus-java,ubschmidt2/instrumentation-java,songy23/instrumentation-java,bogdandrutu/opencensus-java,census-instrumentation/opencensus-java,sebright/instrumentation-java,ubschmidt2/instrumentation-java,bogdandrutu/instrumentation-java,sebright/instrumentation-java,bogdandrutu/opencensus-java,songy23/instrumentation-java,census-instrumentation/opencensus-java,census-instrumentation/opencensus-java,bogdandrutu/opencensus-java,sebright/opencensus-java