[SPARK-16606][MINOR] Tiny follow-up to , to correct more instances of the same log message typo

## What changes were proposed in this pull request?

Tiny follow-up to SPARK-16606 / https://github.com/apache/spark/pull/14533 , to correct more instances of the same log message typo

## How was this patch tested?

Existing tests (no functional change anyway)

Author: Sean Owen <sowen@cloudera.com>

Closes #15586 from srowen/SPARK-16606.2.

sql/core/src/main/scala/org/apache/spark/sql/SparkSession.scala

@@ -814,7 +814,7 @@ object SparkSession {
       if ((session ne null) && !session.sparkContext.isStopped) {
         options.foreach { case (k, v) => session.sessionState.conf.setConfString(k, v) }
         if (options.nonEmpty) {
-          logWarning("Use an existing SparkSession, some configuration may not take effect.")
+          logWarning("Using an existing SparkSession; some configuration may not take effect.")
         }
         return session
       }
@@ -826,7 +826,7 @@ object SparkSession {
         if ((session ne null) && !session.sparkContext.isStopped) {
           options.foreach { case (k, v) => session.sessionState.conf.setConfString(k, v) }
           if (options.nonEmpty) {
-            logWarning("Use an existing SparkSession, some configuration may not take effect.")
+            logWarning("Using an existing SparkSession; some configuration may not take effect.")
           }
           return session
         }