Upgrade ipywidgets to 7.6.3

[mkoeppe]

... to latest version 7.6.3 (released Jan 2021)

(widgetsnbextension is still current.)

The previous upgrade was done as part of #26919.

This is also preparation for #31278.

CC: @kiwifb @isuruf @antonio-rojas @jcamp0x2a @jhpalmieri @slel

Component: packages: standard

Author: Matthias Koeppe

Branch/Commit: a8035aa

Reviewer: Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/31328

[mkoeppe]

Description changed:

--- 
+++ 
@@ -1 +1,4 @@
+... to latest version 7.6.3 (released Jan 2021)
 
+(`widgetsnbextension` is still current.)
+

[mkoeppe]

Branch: u/mkoeppe/upgrade_ipywidgets__widgetsnbextension

[mkoeppe]

Commit: a8035aa

[mkoeppe]

New commits:

a8035aa

build/pkgs/ipywidgets: Upgrade to 7.6.3

[mkoeppe]

Author: Matthias Koeppe

[mkoeppe]

Description changed:

--- 
+++ 
@@ -2,3 +2,7 @@
 
 (`widgetsnbextension` is still current.)
 
+The previous upgrade was done as part of #26919.
+
+This is also preparation for #31278.
+

[dimpase]

Reviewer: Dima Pasechnik

[dimpase]

comment:5

lgtm

[mkoeppe]

comment:6

Thanks!

[vbraun]

Changed branch from u/mkoeppe/upgrade_ipywidgets__widgetsnbextension to a8035aa