fix: remove leftover near_sdk::__private::schemars

[dj8yfo]

this prevents compiling sample contract

use near_sdk::borsh::{BorshDeserialize, BorshSerialize};
use near_sdk::near_bindgen;
#[near_bindgen]
#[derive(Default, BorshDeserialize, BorshSerialize)]
#[borsh(crate = "near_sdk::borsh")]
pub struct Contract {}
#[near_bindgen]
impl Contract {
    pub fn foo(&self, a: bool, b: u32) {}
}

with cargo build --features "near-sdk/__abi-generate"