Imroved Prefab] Override indicator(Blue line) appears misaligned on Mode property in "Sky and Fog Volume" prefab instance.

Override indicator(Blue line) appears misaligned on Mode property in "Sky and Fog Volume" prefab instance.

Steps to repro:
1. Create a new HDRP Project.
2. Hierarchy > Right Click > Volume > Sky and Fog Volume > Create its Prefab.
3. Select Sky and Fog Volume > Change Mode property to Local.

Actual Result:
Override indicator(Blue line) appears misaligned on Mode property.

Expected Result:
Override indicator(Blue line) appears properly in front of Mode property.

Reproducible in:
2020.2.0a10, 2020.1.0b8, 2019.3.0f3 with Package version 9.0.0, 8.1.0, 8.0.1, 7.1.8.

Environment:
Occurring on Windows 10 & Mac 10.15

Note: Bug is in VolumeEditor.cs; see details in comment.