docs: give this config a more detailed explanation

config.example.toml

@@ -103,7 +103,10 @@
 # enable_pipupgrade = true                         ###disabled by default
 # pipupgrade_arguments = "-y -u --pip-path pip"    ###disabled by default
 
-# Run `poetry self update` even if poetry was not installed with the official script
+# For the poetry step, by default, Topgrade skips its update if poetry is not 
+# installed with the official script. This configuration entry forces Topgrade 
+# to run the update in this case.
+#
 # (default: false)
 # poetry_force_self_update = true