docs: adds Model#count to list of fns callback removed from

[SethFalco]

Summary

I'm working on migrating from Mongoose v6 to Mongoose v7. Part of this includes dropping all callbacks in favor of Promises.

I noticed that Model#count and Query#count is not in the list though, which according to the types, had a callback param in v6, which was removed in v7. This should be in the list of functions as well that the callback param was removed from too.

(Also fixes a petty typo as well, since I was modifying this file anyway.)

Examples

N/A

[vkarpov15]

Reasonable enough. I guess since count() was removed, we can also say that the callback was removed. Thanks 👍

[SethFalco]

The count() function was removed in v8, not v7 which is what this change is for! Only the callback was removed in v7. (I'm still a bit behind on versions, but upgrading 1 major version at a time. ^-^')