Fix SyntaxWarning where 'is' is used rather than '=='

[PureTryOut]

Without this MR at least Python 3.8 will complain:

/usr/lib/python3.8/site-packages/lingua_franca/lang/format_en.py:293: SyntaxWarning: "is" with a literal. Did you mean "=="?
  if abs(num) < 1.0 and (result is "minus " or not result):
/usr/lib/python3.8/site-packages/lingua_franca/lang/format_pt.py:108: SyntaxWarning: "is" with a literal. Did you mean "=="?
  if abs(num) < 1.0 and (result is "menos " or not result):
/usr/lib/python3.8/site-packages/lingua_franca/lang/format_it.py:387: SyntaxWarning: "is" with a literal. Did you mean "=="?
  if abs(num) < 1.0 and (result is "meno " or not result):
/usr/lib/python3.8/site-packages/lingua_franca/lang/format_es.py:197: SyntaxWarning: "is" with a literal. Did you mean "=="?
  if abs(num) < 1.0 and (result is "menos " or not result):
/usr/lib/python3.8/site-packages/lingua_franca/lang/format_fr.py:195: SyntaxWarning: "is" with a literal. Did you mean "=="?
  if abs(num) < 1.0 and (result is "moins " or not result):
/usr/lib/python3.8/site-packages/lingua_franca/lang/parse_en.py:404: SyntaxWarning: "is" with a literal. Did you mean "=="?
  if ordinals and prev_word in string_num_ordinal and val is 1:

[ChanceNCounter]

Looks good. I'm gonna tag "don't merge" for a couple days so that we can merge this onto an anticipated refactor, rather than rebasing that huge branch for what would be the third time.

But, otherwise, looks correct at first glance.