Remove unused lib

Author: Siedlerchr

external-libraries.txt

@@ -241,9 +241,4 @@ Project: latex2unicode
 URL:     https://github.com/tomtung/latex2unicode
 License: Apache 2.0
 
-Id:      com.github.wnameless
-Project: json-flattener
-URL:     https://github.com/tomtung/latex2unicode
-License: Apache 2.0
-
 The last entry has to end with an empty line. Otherwise the entry is not present in About.html.