No completion in strings, text blocks, comments, or Javadoc

- Javadoc will need to be revisited, but for now I turned off the
  default completion

Signed-off-by: David Thompson <davthomp@redhat.com>

org.eclipse.jdt.core/codeassist/org/eclipse/jdt/internal/codeassist/DOMCompletionEngine.java

@@ -292,6 +292,9 @@ public void run() {
 
 			checkCancelled();
 
+			if (context instanceof StringLiteral || context instanceof TextBlock || context instanceof Comment || context instanceof Javadoc) {
+				return;
+			}
 			if (context instanceof FieldAccess fieldAccess) {
 				statementLikeKeywords();
 
@@ -592,6 +595,9 @@ public void run() {
 				}
 				suggestDefaultCompletions = false;
 			}
+			if (context instanceof Javadoc) {
+				suggestDefaultCompletions = false;
+			}
 
 			// check for accessible bindings to potentially turn into completions.
 			// currently, this is always run, even when not using the default completion,