[MINOR][EXAMPLES] Add missing return keyword streaming word count example

This is a very low level error.

Closes apache#24153 from jiangruocheng/master.

Authored-by: Ruocheng Jiang <[email protected]>
Signed-off-by: Sean Owen <[email protected]>

Author: jiangruocheng

examples/src/main/python/streaming/recoverable_network_wordcount.py

@@ -83,9 +83,9 @@ def echo(time, rdd):
         def filterFunc(wordCount):
             if wordCount[0] in blacklist.value:
                 droppedWordsCounter.add(wordCount[1])
-                False
+                return False
             else:
-                True
+                return True
 
         counts = "Counts at time %s %s" % (time, rdd.filter(filterFunc).collect())
         print(counts)