Bug in the computeQ function - v2 classifier

Describe the issue
In the [computeQ](https://github.com/google/licenseclassifier/blob/3043a050f148a588e7e0c84dce27579dfe17fd2d/v2/document.go#L74) when the threshold is set to `1.0` the granularity is being calculated as `10`, but if we set the threshold to `0.95`, `0.99`, or `0.999` the granularity is being calculated as `19`, `99`, `999`, respectively where there is exponential growth and also the granularity is greater than the granularity set at `maxThresold`(1.0) which is 10.

Is this intentional?

A problem occurring due to this issue is that when we set the threshold to `0.95` or greater a lot of licenses are not being detected which in the case we set to `0.9` are easily being detected.

I ran the program for around `17,300` license files out of which around `2950 BSD-3-Clause`, `850 BSD-2-Clause` and some other licenses were not at all detected which were otherwise detected at a granularity of `10` because at that threshold the granularity is greater than 20 and nearly reaches 100.

A possible solution would be to set the granularity to `10` for a threshold greater than `0.9` and it will also handle the divide by zero cases.