Drop old enum syntax. Comma / semicolon are now a syntactic part of enum entry.

Comma must present now between enum entries, semicolon between last entry & first member, constructor calls must be without colons / specifiers.
A swarm of tests fixed accordingly.

compiler/testData/psi/SoftKeywords.kt

@@ -5,7 +5,6 @@ import foo
 public protected private internal
 abstract
 open
-enum
 open
 annotation
 override