Fix: hazard curve tool tip tweaks

[chrisdicaprio]

On the /Hazardcurves page:

• The tooltip for PoE should read "The probability of experiencing an acceleration (g) or more within the next T years where T is the chosen Time Period. See the Technical Info Page for more detail.
• The tooltip for vs30 should read: "Vs30 is the time-averaged shear wave velocity in top 30m beneath the site. Use a Vs30 value estimated for your site. The NSHM does not include a national Vs30 map."