docs: Label table columns as "CPython output" and "MicroPython output".

Abbreviating these doesn't really save space in the docs, as the code
blocks in the next row are always wider than the column headings.

Signed-off-by: Angus Gratton <angus@redyak.com.au>

Author: projectgus

tools/gen-cpydiff.py

@@ -260,7 +260,7 @@ def gen_rst(results):
         output_cpy = ("::\n\n" if output_cpy != "" else "") + output_cpy
         output_upy = indent(output.output_upy, TAB).rstrip()
         output_upy = ("::\n\n" if output_upy != "" else "") + output_upy
-        table = gen_table([["CPy output:", output_cpy], ["uPy output:", output_upy]])
+        table = gen_table([["CPython output:", output_cpy], ["MicroPython output:", output_upy]])
         rst.write(table)
 
     template = open(INDEXTEMPLATE, "r")