Upgrade datashader to newest version and pick up single category fix. ran into issue where categorie '' already existed

Author: Sean Sullivan

elastic_datashader/tilegen.py

@@ -1273,10 +1273,6 @@ def remap_bucket(bucket, search):
             except ValueError:
                 pass
 
-            # datashader has issue in 0.15.0 with categories that have only one class
-            # https://github.com/holoviz/datashader/issues/1230
-            if len(categories) == 1:
-                categories.append('')
             cat_dtype = pd.api.types.CategoricalDtype(categories=categories, ordered=True)
             df["t"] = df["t"].astype(cat_dtype)
 

pyproject.toml

@@ -23,7 +23,7 @@ elastic_datashader = "elastic_datashader.cli:main"
 python = ">=3.10,<4"
 elasticsearch = "7.17.4"
 elasticsearch-dsl = "7.4.0"
-datashader = "0.15.0"
+datashader = "0.15.2"
 pandas = "^1.5.3"
 colorcet = "^3.0.1"
 mercantile = "1.2.1"