[MINOR][CORE] Fix a duplicate "and" in a log message.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #11642 from vanzin/spark-conf-typo.

core/src/main/scala/org/apache/spark/SparkConf.scala

@@ -718,7 +718,7 @@ private[spark] object SparkConf extends Logging {
     allAlternatives.get(key).foreach { case (newKey, cfg) =>
       logWarning(
         s"The configuration key '$key' has been deprecated as of Spark ${cfg.version} and " +
-        s"and may be removed in the future. Please use the new key '$newKey' instead.")
+        s"may be removed in the future. Please use the new key '$newKey' instead.")
       return
     }
     if (key.startsWith("spark.akka") || key.startsWith("spark.ssl.akka")) {