[MINOR] Ignore python/lib/pyspark.zip

Add `python/lib/pyspark.zip` to `.gitignore`. After merging apache#5580, `python/lib/pyspark.zip` will be generated when building Spark.

Author: zsxwing <zsxwing@gmail.com>

Closes apache#6017 from zsxwing/gitignore and squashes the following commits:

39b10c4 [zsxwing] Ignore python/lib/pyspark.zip

.gitignore

@@ -65,6 +65,7 @@ scalastyle.txt
 scalastyle-output.xml
 R-unit-tests.log
 R/unit-tests.out
+python/lib/pyspark.zip
 
 # For Hive
 metastore_db/