avro

Fix whitespace in CodeGen::generateEnumTraits to be consistent with the rest of the generated code. (#1034)

avrogencpp has tabs in CodeGen::generateEnumTraits, which is inconsistent with the rest of the generated code. (#1034)

This commit replaces all of the tabs in the CodeGen::generateEnumTraits function with 4 spaces to match the formatting of the rest of the file as well as the rest of the generated code

Co-authored-by: Allen Reese <areese999@apple.com>