Although there was no docblock on CaptchaAuthenticationRequest::__construct,
the method is supposed to get a string and an array, as that's how the
class members are documented and used. Trying to access offsets of null
resulted in PHP notices on PHP 7.4, as seen in the experimental job
for various repos.
Bug: T239726
Change-Id: Idd073ebf3d560543ec225479de060e3c198847eb
Also remove references to "two words" from ReCaptcha labels.
The captcha image doesn't always contain two words.
Bug: T110302
Change-Id: I544656289480056152a1db195babb6dadf29bc71
Also update MathCaptcha so that it works with recent versions of
Math (and breaks with old ones). Also fix MathCaptcha API output,
which used to send the question in plaintext.
Bug: T110302
Change-Id: I0da671a546700110d789b79a3089460abd9cce3b
Depends-On: I8b52ec8ddf494f23941807638f149f15b5e46b0c
