[MINOR][PYTHON] Fix spacing in error message

### What changes were proposed in this pull request?
Fixes spacing in an error message

### Why are the changes needed?
Makes error messages easier to read

### Does this PR introduce _any_ user-facing change?
Yes, it changes the error message

### How was this patch tested?
This patch doesn't affect any logic, so existing tests should cover it

Closes apache#29264 from hauntsaninja/patch-1.

Authored-by: Shantanu <12621235+hauntsaninja@users.noreply.github.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>

python/pyspark/worker.py

@@ -468,7 +468,7 @@ def main(infile, outfile):
         version = utf8_deserializer.loads(infile)
         if version != "%d.%d" % sys.version_info[:2]:
             raise Exception(("Python in worker has different version %s than that in " +
-                             "driver %s, PySpark cannot run with different minor versions." +
+                             "driver %s, PySpark cannot run with different minor versions. " +
                              "Please check environment variables PYSPARK_PYTHON and " +
                              "PYSPARK_DRIVER_PYTHON are correctly set.") %
                             ("%d.%d" % sys.version_info[:2], version))