docs: update calendar and link releases notes for 20.1.7

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6573>
diff --git a/docs/relnotes.rst b/docs/relnotes.rst
index 8883065..e623b52 100644
--- a/docs/relnotes.rst
+++ b/docs/relnotes.rst
@@ -3,6 +3,7 @@
 
 The release notes summarize what's new or changed in each Mesa release.
 
+-  :doc:`20.1.7 release notes <relnotes/20.1.7>`
 -  :doc:`20.1.6 release notes <relnotes/20.1.6>`
 -  :doc:`20.1.5 release notes <relnotes/20.1.5>`
 -  :doc:`20.1.4 release notes <relnotes/20.1.4>`
@@ -312,6 +313,7 @@
    :maxdepth: 1
    :hidden:
 
+   relnotes/20.1.7
    relnotes/20.1.6
    relnotes/20.1.5
    relnotes/20.1.4