Revert "fix: update test_arrow_cast to cast literals to string type for arrow_cast function"

This reverts commit 856ff8c.

Author: kosiew

python/tests/test_functions.py

@@ -23,7 +23,7 @@
 
 from datafusion import SessionContext, column
 from datafusion import functions as f
-from datafusion import literal, expr
+from datafusion import literal
 
 np.seterr(invalid="ignore")
 
@@ -907,10 +907,8 @@ def test_temporal_functions(df):
 
 def test_arrow_cast(df):
     df = df.select(
-        f.arrow_cast(column("a"), literal("Float64").cast(pa.string())).alias(
-            "a_as_float"
-        ),
-        f.arrow_cast(column("a"), literal("Int32").cast(pa.string())).alias("a_as_int"),
+        f.arrow_cast(column("a"), literal("Float64")).alias("a_as_float"),
+        f.arrow_cast(column("a"), literal("Int32")).alias("a_as_int"),
     )
     result = df.collect()
     assert len(result) == 1