updated about files specification link

Signed-off-by: Naveen-singla <Naveensigla2001@gmail.com>

Author: Naveen-singla

docs/source/aboutcode-toolkit/home.rst

@@ -31,9 +31,8 @@ In addition, this tool is able to generate attribution notices and
 identify redistributable source code used in your project to help you comply
 with open source licenses conditions.
 
-This version of the AboutCode Toolkit follows the ABOUT specification version 3.0 at:
-https://github.com/nexB/aboutcode-toolkit/blob/develop/SPECIFICATION.rst
-
+This version of the AboutCode Toolkit follows the ABOUT specification version 3.1.2 at:
+https://aboutcode-toolkit.readthedocs.io/en/latest/specification.html
 
 REQUIREMENTS
 ------------