Fix compilation warnings related to other-nullary-override

[error] /Users/yangjie01/SourceCode/git/spark-mine-sbt/connector/connect/common/src/main/scala/org/apache/spark/sql/connect/client/CloseableIterator.scala:36:16: method with a single empty parameter list overrides method hasNext in trait Iterator defined without a parameter list [quickfixable]
[error] Applicable -Wconf / @nowarn filters for this fatal warning: msg=<part of the message>, cat=other-nullary-override, site=org.apache.spark.sql.connect.client.WrappedCloseableIterator
[error]   override def hasNext(): Boolean = innerIterator.hasNext
[error]                ^
[error] /Users/yangjie01/SourceCode/git/spark-mine-sbt/connector/connect/common/src/main/scala/org/apache/spark/sql/connect/client/ExecutePlanResponseReattachableIterator.scala:136:16: method without a parameter list overrides method hasNext in class WrappedCloseableIterator defined with a single empty parameter list [quickfixable]
[error] Applicable -Wconf / @nowarn filters for this fatal warning: msg=<part of the message>, cat=other-nullary-override, site=org.apache.spark.sql.connect.client.ExecutePlanResponseReattachableIterator
[error]   override def hasNext: Boolean = synchronized {
[error]                ^
[error] /Users/yangjie01/SourceCode/git/spark-mine-sbt/connector/connect/common/src/main/scala/org/apache/spark/sql/connect/client/GrpcExceptionConverter.scala:73:20: method without a parameter list overrides method hasNext in class WrappedCloseableIterator defined with a single empty parameter list [quickfixable]
[error] Applicable -Wconf / @nowarn filters for this fatal warning: msg=<part of the message>, cat=other-nullary-override, site=org.apache.spark.sql.connect.client.GrpcExceptionConverter.convertIterator
[error]       override def hasNext: Boolean = {
[error]                    ^
[error] /Users/yangjie01/SourceCode/git/spark-mine-sbt/connector/connect/common/src/main/scala/org/apache/spark/sql/connect/client/GrpcRetryHandler.scala:77:18: method without a parameter list overrides method next in class WrappedCloseableIterator defined with a single empty parameter list [quickfixable]
[error] Applicable -Wconf / @nowarn filters for this fatal warning: msg=<part of the message>, cat=other-nullary-override, site=org.apache.spark.sql.connect.client.GrpcRetryHandler.RetryIterator
[error]     override def next: U = {
[error]                  ^
[error] /Users/yangjie01/SourceCode/git/spark-mine-sbt/connector/connect/common/src/main/scala/org/apache/spark/sql/connect/client/GrpcRetryHandler.scala:81:18: method without a parameter list overrides method hasNext in class WrappedCloseableIterator defined with a single empty parameter list [quickfixable]
[error] Applicable -Wconf / @nowarn filters for this fatal warning: msg=<part of the message>, cat=other-nullary-override, site=org.apache.spark.sql.connect.client.GrpcRetryHandler.RetryIterator
[error]     override def hasNext: Boolean = {
[error]                  ^