MINOR: Fixed a few typos in configs and streams docs (#4452)

Reviewers: Guozhang Wang <wangguoz@gmail.com>

config/server.properties

@@ -56,7 +56,7 @@ socket.request.max.bytes=104857600
 
 ############################# Log Basics #############################
 
-# A comma seperated list of directories under which to store log files
+# A comma separated list of directories under which to store log files
 log.dirs=/tmp/kafka-logs
 
 # The default number of log partitions per topic. More partitions allow greater