Clamp water setting: Blur Multiplier values in the UI

[AtlasLinden]

Environment

Second Life Release 7.1.12.13509103967 (ForeverFPS)

Description

As mentioned in #3655, clamp the values so that only positive Blur Multiplier values can be applied.

Reproduction steps

Open a water setting.
Observe Blur Multiplier slider

[canny]

This issue has been linked to a Canny post: Broken blur multiplier after the "fix" 🎉

[AtlasLinden]

Passed QA.
Verified on the Second Life Release 7.1.13.14542338120 (2025.04) on Win11/MacOS

It is no longer possible to set a negative blur multiplier value via the UI.
Water settings that previously used a negative blur multiplier now have this value set to 0.
In 7.X builds, the negative blur multiplier doesn't have any effect as given in #3655 mentioned above.
Please note that the Blur Multipliers negative values did have some effect in pre-PBR viewers.