fix: don't override paths in dockerfile

This allows for these paths to continue to be set in the config file or environment variable while still maintaining the default of having the default paths in the same directory as the postal config file.

Gemfile.lock

@@ -149,7 +149,7 @@ GEM
       concurrent-ruby (>= 1.0, < 2.0)
       json
       rouge (>= 3.30, < 5.0)
-    konfig-config (2.1.1)
+    konfig-config (3.0.0)
       hashie
     loofah (2.22.0)
       crass (~> 1.0.2)
@@ -353,7 +353,7 @@ DEPENDENCIES
   jquery-rails
   kaminari
   klogger-logger
-  konfig-config (~> 2.0)
+  konfig-config (~> 3.0)
   mail
   moonrope
   mysql2