doc/go1.14: document that Go 1.14 is likely last to support darwin/arm

Fixes #34751

Change-Id: I5ae1bb2bfddaa05245b364556d2b999b158a4cc4
Reviewed-on: https://go-review.googlesource.com/c/go/+/203879Reviewed-by: Bryan C. Mills <bcmills@google.com>

doc/go1.14.html

@@ -56,6 +56,14 @@ TODO
   Go 1.14 is the last Go release to support 32-bit binaries on
   macOS (the <code>darwin/386</code> port). They are no longer
   supported by macOS, starting with macOS 10.15 (Catalina).
+  Go continues to support the 64-bit <code>darwin/amd64</code> port.
+</p>
+
+<p><!-- golang.org/issue/34751 -->
+  Go 1.14 will likely be the last Go release to support 32-bit
+  binaries on iOS, iPadOS, watchOS, and tvOS
+  (the <code>darwin/arm</code> port). Go continues to support the
+  64-bit <code>darwin/arm64</code> port.
 </p>
 
 <h3 id="nacl">Native Client (NaCl)</h3>