Fix value flow for fluent api

Author: Benjamin Muskalla

java/ql/lib/semmle/code/java/frameworks/Strings.qll

@@ -39,13 +39,13 @@ private class StringSummaryCsv extends SummaryModelCsv {
         "java.lang;String;false;valueOf;(char[],int,int);;Argument[0];ReturnValue;taint",
         "java.lang;String;false;valueOf;(char[]);;Argument[0];ReturnValue;taint",
         "java.io;StringWriter;true;append;;;Argument[0];Argument[-1];taint",
-        "java.io;StringWriter;true;append;;;Argument[-1];ReturnValue;taint",
+        "java.io;StringWriter;true;append;;;Argument[-1];ReturnValue;value",
         "java.io;StringWriter;true;write;;;Argument[0];Argument[-1];taint",
         "java.lang;AbstractStringBuilder;true;AbstractStringBuilder;(String);;Argument[0];Argument[-1];taint",
         "java.lang;AbstractStringBuilder;true;append;;;Argument[0];Argument[-1];taint",
         "java.lang;AbstractStringBuilder;true;append;;;Argument[-1];ReturnValue;value",
         "java.lang;AbstractStringBuilder;true;insert;;;Argument[1];Argument[-1];taint",
-        "java.lang;AbstractStringBuilder;true;insert;;;Argument[-1];ReturnValue;taint",
+        "java.lang;AbstractStringBuilder;true;insert;;;Argument[-1];ReturnValue;value",
         "java.lang;AbstractStringBuilder;true;replace;;;Argument[-1];ReturnValue;value",
         "java.lang;AbstractStringBuilder;true;replace;;;Argument[2];Argument[-1];taint",
         "java.lang;AbstractStringBuilder;true;toString;;;Argument[-1];ReturnValue;taint",