While you generally want to take 4 years
of the core subjects including foreign language in high school it’s not a hard and fast rule.
My gap year D20 Duke kid only took two years of Spanish in high school (and the last year was taken in the summer not affiliated with the school.). But she also had a pretty rigorous schedule with 8 AP classes and 3 honors classs as well as a varsity sport, student board school district rep, and academic decathlon.
She also never took an AP science class other than AP environmental science as she had honors biology and honors chemistry and took a regular physics class at UCLA.
My point is that if the rest if your “resume” and application is strong it’s probably ok not to have all 4 years of one subject.
With that said, D now wants to take Spanish all 4 years in college so in hindsight it would have been good for her to have continued the progression all four years in high school.