[feat] Remove expensive and unmaintained zxcvbn-go strength checker

[twpayne]

Fixes #3132.

Improves start-up time by 533%.

Before:

$ time ./gopass --version
gopass 1.15.15-git+HEAD (a27a9cc1) go1.24.2 linux amd64
./gopass --version  0.03s user 0.01s system 130% cpu 0.032 total

After:

$ time ./gopass --version
gopass 1.15.15-git+HEAD (3ebb1a7b) go1.24.2 linux amd64
./gopass --version  0.00s user 0.00s system 112% cpu 0.006 total

[dominikschulz]

Very nice cleanup & improvement. Thanks. Let me just try to reproduce the issue, then we can merge this.