CompatHelper: bump compat for "Images" to "0.21" (#42)

Author: github-actions[bot]

Project.toml

@@ -20,7 +20,7 @@ Clustering = "0.10, 0.11, 0.12, 0.13"
 DataStructures = "0.12, 0.13, 0.14, 0.15, 0.16, 0.17"
 Distances = "0.8"
 ImageFiltering = "0.6"
-Images = "0.18, 0.19, 0.20"
+Images = "0.18, 0.19, 0.20, 0.21"
 LightGraphs = "1.1"
 RegionTrees = "0.2, 0.3"
 SimpleWeightedGraphs = "1"