Add "pin" to password-word-equivalents (Bug#35523)

* lisp/international/mule-conf.el (password-word-equivalents): Add "pin".
* test/lisp/comint-tests.el (comint-testsuite-password-strings): Add
test case.
1 job for master in 3 seconds (queued for 1 second)
Status Job ID Name Coverage
failed #2026


Name Stage Failure
test-all Test There has been a runner system failure, please try again
Running with gitlab-runner 11.6.0 (f100a208)
on gitlab-runner-docker cff9d373
Using Docker executor with image debian:stretch ...
Pulling docker image debian:stretch ...
Using docker image sha256:8d31923452f8b79ae91b01568d28c90e7d667a9eaff9734c6faeb017b0efa8d0 for debian:stretch ...
ERROR: Job failed (system failure): Error response from daemon: failed to start shim: exec: "docker-containerd-shim": executable file not found in $PATH: unknown (executor_docker.go:1018:0s)