are_equivalent: remove redundant code

* spot/twacube_algos/convert.cc: Here.
9 jobs for er/spot3 in 91 minutes and 15 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #93630
alpine-gcc

00:56:24

passed #93631
arch-clang

00:46:56

passed #93632
arch-gcc-glibcxxdebug

01:17:01

passed #93629
debian-gcc-snapshot

01:24:25

passed #93627
debian-stable-gcc

01:00:18

passed #93628
debian-unstable-gcc-coverage

01:20:06

89.6%
passed #93633
mingw-shared

00:10:57

passed #93634
mingw-static

00:09:09

passed #93635
armv7
raspbian

01:31:11