Revert "K2/Java: add private enum constructor for MPP matching"

Review: https://jetbrains.team/p/kt/reviews/13368/timeline

This reverts commit 2cea2b9098.

Motivation:
KT-62961 was fixed independently by two different commits:
- ac3d8ad3ac
- 2cea2b9098

If possible, it's better not to introduce implicit declarations.
That's why it was agreed to keep
ac3d8ad3ac and revert
2cea2b9098

compiler/testData/loadJava/compiledJava/enum/JavaEnum.fir.txt

@@ -10,6 +10,4 @@ public final enum class JavaEnum : R|kotlin/Enum<test/JavaEnum!>| {
     public final static val entries: R|kotlin/enums/EnumEntries<test/JavaEnum>|
         public get(): R|kotlin/enums/EnumEntries<test/JavaEnum>|
 
-    private constructor(): R|test/JavaEnum|
-
 }