Revert "Identify data classes during extraction"

This reverts commit a61ba65c9f2182a578a7f4dbdb1c1657197f16cd, pending
adding a proper upgrade script for the DB change.

java/ql/lib/config/semmlecode.dbscheme

@@ -1232,7 +1232,3 @@ ktFunctionOriginalNames(
   unique int id: @method ref,
   string name: string ref
 )
-
-ktDataClasses(
-  unique int id: @class ref
-)

java/ql/lib/semmle/code/java/Type.qll

@@ -714,13 +714,6 @@ class CompanionObject extends Class {
   Field getInstance() { type_companion_object(_, result, this) }
 }
 
-/**
- * A Kotlin data class declaration.
- */
-class DataClass extends Class {
-  DataClass() { ktDataClasses(this) }
-}
-
 /**
  * A record declaration.
  */

java/ql/test/kotlin/library-tests/data-classes/data_classes.expected

@@ -1 +0,0 @@
-| dc.kt:1:1:1:71 | ProtoMapValue |

java/ql/test/kotlin/library-tests/data-classes/data_classes.ql

@@ -1,5 +0,0 @@
-import java
-
-from DataClass c
-where c.fromSource()
-select c