[MINOR][DOCS] Fix the variable name in the docs - testing_pyspark.ipynb
### What changes were proposed in this pull request?
I'm changing a variable name in one of the cells in the documentation regarding pyspark testing.
### Why are the changes needed?
Currently the code won't run. This simple fix will make the code in the documenatatnion usable.
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
I tested this code loccally with pytest and pyspark 3.5.0

### Was this patch authored or co-authored using generative AI tooling?
No
Closes #43610 from huciaa/fix_typo_in_pystest_doc.
Authored-by: huciaa <hubert.kaczmarczyk@pm.me>
Signed-off-by: Hyukjin Kwon <gurwls223@apache.org>
diff --git a/python/docs/source/getting_started/testing_pyspark.ipynb b/python/docs/source/getting_started/testing_pyspark.ipynb
index afccbe4..3934c11 100644
--- a/python/docs/source/getting_started/testing_pyspark.ipynb
+++ b/python/docs/source/getting_started/testing_pyspark.ipynb
@@ -318,7 +318,7 @@
" {\"name\": \"Eve A.\", \"age\": 28}] \n",
" \n",
" # Create a Spark DataFrame\n",
- " original_df = spark.createDataFrame(sample_data)\n",
+ " original_df = spark_fixture.createDataFrame(sample_data)\n",
" \n",
" # Apply the transformation function from before\n",
" transformed_df = remove_extra_spaces(original_df, \"name\")\n",
@@ -328,7 +328,7 @@
" {\"name\": \"Bob T.\", \"age\": 35}, \n",
" {\"name\": \"Eve A.\", \"age\": 28}]\n",
" \n",
- " expected_df = spark.createDataFrame(expected_data)\n",
+ " expected_df = spark_fixture.createDataFrame(expected_data)\n",
"\n",
" assertDataFrameEqual(transformed_df, expected_df)"
]