CompatHelper: bump compat for "DocStringExtensions" to "0.9"

Author: github-actions[bot]

Project.toml

@@ -1,6 +1,6 @@
-authors = ["Rob J Goedman <goedman@icloud.com>, Max Lapan (@Shmuma)"]
 name = "StatisticalRethinking"
 uuid = "2d09df54-9d0f-5258-8220-54c2a3d4fbee"
+authors = ["Rob J Goedman <goedman@icloud.com>, Max Lapan (@Shmuma)"]
 version = "4.5.2"
 
 [deps]
@@ -40,7 +40,7 @@ AxisKeys = "0.1, 0.2"
 CSV = "0.9, 0.10"
 DataFrames = "1"
 Distributions = "0.25"
-DocStringExtensions = "0.8"
+DocStringExtensions = "0.8, 0.9"
 Documenter = "0.27"
 Formatting = "0.4"
 KernelDensity = "0.6"