fix: remove mention of changing static fields (#509)

That's plain wrong.

docs/developer-guide.md

@@ -212,12 +212,4 @@ be automated, but before that is done those checks should be done manually.
   - verify the JAR size (should be < 3 MB)
 - open the English manual and check the version
 - open the Italian manual and check the version
-- check the 'edge' snap and promote it to stable if it works (https://snapcraft.io/edumips64/releases, needs login)
-
-### Overriding instruction field values
-
-Many instruction class contain static fields. This can be confusing and error-prone. If a concrete instruction
-defines any fields that are defined in parent classes (such as, for example, `OPCODE_VALUE`), it is important that
-the constructor also overrides the value of the same attribute for the superclass, or some methods will not work properly.
-
-This is clearly too convoluted and should be redesigned in a way that makes it impossible to make mistakes.
+- check the 'edge' snap and promote it to stable if it works (https://snapcraft.io/edumips64/releases, needs login)