@Override
    protected int getBackedOffPoolSize(final int curr) {
        return curr + increment;
    }
Returns the new pool size after applying the linear backoff algorithm.
The new pool size is calculated by adding the increment value to the current pool size.

@param curr the current pool size
@return the new pool size after applying the linear backoff
httpclient5/src/main/java/org/apache/hc/client5/http/impl/classic/LinearBackoffManager.java