docs: add a notice whenever a release is the final in a series

Cc: Emil Velikov <emil.velikov@collabora.com>
Cc: Juan A. Suarez Romero <jasuarez@igalia.com>
Signed-off-by: Andres Gomez <agomez@igalia.com>
Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Juan A. Suarez <jasuarez@igalia.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

docs/releasing.html

@@ -272,6 +272,11 @@ It is followed by a brief period (normally 24 or 48 hours) before the actual
 release is made.
 </p>
 
+<p>
+Be aware to add a note to warn about a final release in a series, if
+that is the case.
+</p>
+
 <h2>Terminology used</h2>
 
 <ul><li>Nominated</ul>
@@ -311,6 +316,10 @@ The candidate for the Mesa X.Y.Z is now available. Currently we have:
  - NUMBER nominated (outstanding)
  - and NUMBER rejected patches
 
+[If applicable:
+Note: this is the final anticipated release in the SERIES series. Users are
+encouraged to migrate to the NEXT_SERIES series in order to obtain future fixes.]
+
 BRIEF SUMMARY OF CHANGES
 
 Take a look at section "Mesa stable queue" for more information.
@@ -594,7 +603,8 @@ Something like the following steps will do the trick:
 
 <p>
 Also, edit docs/relnotes.html to add a link to the new release notes,
-edit docs/index.html to add a news entry, and remove the version from
+edit docs/index.html to add a news entry and a note in case of the
+last release in a series, and remove the version from
 docs/release-calendar.html. Then commit and push:
 </p>
 
@@ -610,6 +620,11 @@ docs/release-calendar.html. Then commit and push:
 Use the generated template during the releasing process.
 </p>
 
+<p>
+Again, pay attention to add a note to warn about a final release in a
+series, if that is the case.
+</p>
+
 
 <h1 id="website">Update the mesa3d.org website</h1>