Fixed misleading Metric Log Filters code example

[slangeder]

Changed statistic from "Minimum" to "Sum" so that the alarm is triggered as explained when the log contains a line with the pattern "exception Bar".

[vladgurovich]

I agree that Minimum is an incorrect statistic to use here, but i would argue that Maximum is more appropriate by definition:
Maximum is the highest value observed during the specified period.

So if we want to trigger an alert when there are more pattern matches than a given threshold, we need to look at the Maximum number of matches observed during the specified period.

Its counter-intuitive, but thats what i arrived at by trial and error