Reproduction steps:
1. Open attached project "ProceduralGraphRename"
2. In Project window, open "GraphAsset" asset
3. In Procedural graph window, observe ReferenceHeightMap Texture Asset's name
4. In Project window Assets/A2/LowRes, rename "Foo" to "Renamed"
5. In Procedural Graph window, observe ReferenceHeightMap Texture Asset's name

Expected result: The asset name is updated in Procedural Graph
Actual result: The asset name is not updated in Procedural Graph

Reproducible with: 2019.4.0f1, 2020.1.0b12, 2020.2.0a14 (Procedural Graph 0.8.0-preview)
Could not test with: 2018.4.23f1 (dependency package versions unavailable)

Workaround:
Reopening the Procedural Graph window fixes the issue.