[tado] Revert openhab#16686 (openhab#16793)

Downgrade swagger-codegen-maven-plugin to old version.
Add warning to pom file.

Signed-off-by: Holger Friedrich <mail@holger-friedrich.de>
Signed-off-by: Paul Smedley <paul@smedley.id.au>

bundles/org.openhab.binding.tado/pom.xml

@@ -24,9 +24,12 @@
   <build>
     <plugins>
       <plugin>
+        <!-- when upgrading, carefully compare generated source files in
+          target/generated-sources/swagger/src/main/java/org/openhab/binding/tado/internal/api
+          as 2.4. series created code which lead to runtime errors in the past -->
         <groupId>io.swagger</groupId>
         <artifactId>swagger-codegen-maven-plugin</artifactId>
-        <version>2.4.41</version>
+        <version>2.3.1</version>
         <executions>
           <execution>
             <goals>