cleanup cpdCompat

pmd-core/src/main/java/net/sourceforge/pmd/lang/document/CpdCompat.java

@@ -5,10 +5,8 @@
 package net.sourceforge.pmd.lang.document;
 
 import net.sourceforge.pmd.cpd.SourceCode;
-import net.sourceforge.pmd.lang.Language;
 import net.sourceforge.pmd.lang.LanguageVersion;
-import net.sourceforge.pmd.lang.impl.LanguageModuleBase.LanguageMetadata;
-import net.sourceforge.pmd.lang.impl.SimpleLanguageModuleBase;
+import net.sourceforge.pmd.lang.PlainTextLanguage;
 
 /**
  * Compatibility APIs, to be removed before PMD 7 is out.
@@ -20,18 +18,9 @@ public final class CpdCompat {
         // utility class
     }
 
-
-    /** The language version must be non-null. */
-    @Deprecated
-    private static final Language DUMMY_LANG =
-    new SimpleLanguageModuleBase(LanguageMetadata.withId("dummy").name("dummy").extensions("dummy"),
-                                 props -> () -> task -> {
-                                     throw new UnsupportedOperationException();
-                                 });
-
     @Deprecated
     public static LanguageVersion dummyVersion() {
-        return DUMMY_LANG.getDefaultVersion();
+        return PlainTextLanguage.getInstance().getDefaultVersion();
     }
 
     /**

pmd-core/src/main/java/net/sourceforge/pmd/lang/impl/LanguageModuleBase.java

@@ -147,7 +147,7 @@ public abstract class LanguageModuleBase implements Language {
         return Objects.equals(getId(), other.getId());
     }
 
-    public static final class LanguageMetadata {
+    protected static final class LanguageMetadata {
         private String name;
         private String shortName;
         private final String id;