IN-211558 Added the release notes v31.2.18 node entry in the TOC.html file

Author: DeepakRajSundar

flutter-toc.html

@@ -600,6 +600,7 @@
 			<ul>
 				<li> Weekly Nuget Release 
 				<ul>
+				<li><a href="/flutter/release-notes/v31.2.18">v31.2.18</a></li>
 				<li><a href="/flutter/release-notes/v31.2.16">v31.2.16</a></li>
 				<li><a href="/flutter/release-notes/v31.2.15">v31.2.15</a></li>
 				<li><a href="/flutter/release-notes/v31.2.10">v31.2.10</a></li>