Replaces `iHigh()` and `iLow()` function calls with direct array access on the `rates` buffer inside the `OnTick()` function.
The `rates` array, containing the necessary high and low price data, was already copied into memory at the beginning of the function. The subsequent calls to `iHigh()` and `iLow()` were redundant and added unnecessary function call overhead to a performance-critical path that executes on every price tick.
This change eliminates two function calls from this hot path, resulting in a more efficient Expert Advisor.
