spelling: writing

Signed-off-by: Josh Soref <[email protected]>

docs/source/cpp/examples/compute_and_write_example.rst

@@ -23,6 +23,6 @@ Compute and Write CSV Example
 
 The file ``cpp/examples/arrow/compute_and_write_csv_example.cc`` located inside 
 the source tree contains an example of creating a table of two numerical columns 
-and then comparing the magnitudes of the entries in the columns and wrting out to 
+and then comparing the magnitudes of the entries in the columns and writing out to 
 a CSV file with the column entries and their comparisons.  The code in the example
 is documented.