doc/go1.14: mention better error checking in text/template

This caused 35 test failures in Google internal code,
so it's worth mentioning in the release notes.

Updates golang#31810
Updates golang#36878
Fixes golang#37066

Change-Id: I2faa6bce4c7d735107eceaef7d95223844846454
Reviewed-on: https://go-review.googlesource.com/c/go/+/217978
Reviewed-by: Rob Pike <r@golang.org>

doc/go1.14.html

@@ -823,6 +823,20 @@ <h3 id="minor_library_changes">Minor changes to the library</h3>
     </p>
 </dl><!-- testing -->
 
+<dl id="text/template"><dt><a href="/pkg/text/template/">text/template</a></dt>
+  <dd>
+    <p><!-- CL 206124 -->
+      The text/template package now correctly reports errors when a
+      parenthesized argument is used as a function.
+      This most commonly shows up in erroneous cases like
+      <code>{{if (eq .F "a") or (eq .F "b")}}</code>.
+      This should be written as <code>{{if or (eq .F "a") (eq .F "b")}}</code>.
+      The erroneous case never worked as expected, and will now be
+      reported with an error <code>can't give argument to non-function</code>.
+    </p>
+  </dd>
+</dl><!-- text/template -->
+
 <dl id="unicode"><dt><a href="/pkg/unicode/">unicode</a></dt>
   <dd>
     <p>