Drop obsolete annotations syntax

compiler/testData/psi/recovery/objects/declarations/ConstructorModifiers.kt

@@ -6,4 +6,4 @@ object Foo private () : Bar {
 
 }
 
-object Foo [foo] private [bar()] ()
+object Foo @[foo] private @[bar()] ()

compiler/testData/psi/recovery/objects/declarations/ConstructorModifiers.txt

@@ -72,6 +72,7 @@ JetFile: ConstructorModifiers.kt
     PRIMARY_CONSTRUCTOR
       MODIFIER_LIST
         ANNOTATION
+          PsiElement(AT)('@')
           PsiElement(LBRACKET)('[')
           ANNOTATION_ENTRY
             CONSTRUCTOR_CALLEE
@@ -84,6 +85,7 @@ JetFile: ConstructorModifiers.kt
         PsiElement(private)('private')
         PsiWhiteSpace(' ')
         ANNOTATION
+          PsiElement(AT)('@')
           PsiElement(LBRACKET)('[')
           ANNOTATION_ENTRY
             CONSTRUCTOR_CALLEE

compiler/testData/psi/recovery/objects/declarations/FollowedByModifiers.kt

@@ -4,4 +4,4 @@ public class Bar
 
 object Foo
 
-[foo] class Bar
+@[foo] class Bar

compiler/testData/psi/recovery/objects/declarations/FollowedByModifiers.txt

@@ -26,6 +26,7 @@ JetFile: FollowedByModifiers.kt
   CLASS
     MODIFIER_LIST
       ANNOTATION
+        PsiElement(AT)('@')
         PsiElement(LBRACKET)('[')
         ANNOTATION_ENTRY
           CONSTRUCTOR_CALLEE