#187 - Update sp_PressureDetector.sql

[samplesty]

Modify query for total memory to support Azure SQL DB

[samplesty]

PR for Issue #187

[erikdarlingdata]

When I run these two queries locally, there's a pretty big difference in the results:

Yours seems to under-report by about 8GB. I re-wrote the check a slightly different way to avoid that, and will incorporate it into a future release.