words: redress historical wrongs against the tuatara

b5a41ff381bf originally added both tuatara and mispelled tautara,
one as a tail and one as a scale.

f174ecb6fdab added tuatara as a scale, not noticing the tautara
imposter.

Fixes #20522

Change-Id: Ie4fcb262ac705c766f55d406835de419856bb170
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>