CONTRIBUTORS: Update per-contributor hyperlinks

In commit 2f852580fb (CONTRIBUTORS: Improve formatting of
per-contributor hyperlinks, 2025-03-02) we accidentally added `mailto:`
on a few URLs that should use `https://` instead.

Reported-by: Rolf Eike Beer <[email protected]>

CONTRIBUTORS.rst

@@ -32,8 +32,8 @@ The following individuals and institutions are among the contributors:
 * Gregor Jasny
 * `Helio Chissini de Castro <mailto:[email protected]>`_
 * `Ilya Lavrenov <mailto:[email protected]>`_
-* `Insight Software Consortium <mailto:insightsoftwareconsortium.org>`_
-* `Intel Corporation <mailto:www.intel.com>`_
+* `Insight Software Consortium <https://insightsoftwareconsortium.org/>`_
+* `Intel Corporation <https://www.intel.com/>`_
 * Jan Woetzel
 * `Jordan Williams <mailto:[email protected]>`_
 * Julien Schueller
@@ -46,7 +46,7 @@ The following individuals and institutions are among the contributors:
 * Matthaeus G. Chajdas
 * `Matthias Kretz <mailto:[email protected]>`_
 * `Matthias Maennich <mailto:[email protected]>`_
-* `Michael Hirsch, Ph.D. <mailto:www.scivision.co>`_
+* `Michael Hirsch, Ph.D. <https://www.scivision.dev/>`_
 * Michael Stürmer
 * Miguel A. Figueroa-Villanueva
 * `Mike Durso <mailto:[email protected]>`_
@@ -55,8 +55,8 @@ The following individuals and institutions are among the contributors:
 * `Nicolas Bock <mailto:[email protected]>`_
 * `Nicolas Despres <mailto:[email protected]>`_
 * `Nikita Krupen'ko <mailto:[email protected]>`_
-* `NVIDIA Corporation <mailto:www.nvidia.com>`_
-* `OpenGamma Ltd. <mailto:opengamma.com>`_
+* `NVIDIA Corporation <https://www.nvidia.com/>`_
+* `OpenGamma Ltd. <https://opengamma.com/>`_
 * `Patrick Stotko <mailto:[email protected]>`_
 * `Per Øyvind Karlsen <mailto:[email protected]>`_
 * `Peter Collingbourne <mailto:[email protected]>`_
@@ -64,7 +64,7 @@ The following individuals and institutions are among the contributors:
 * `Philip Lowman <mailto:[email protected]>`_
 * `Philippe Proulx <mailto:[email protected]>`_
 * Raffi Enficiaud, Max Planck Society
-* `Raumfeld <mailto:raumfeld.com>`_
+* Raumfeld
 * `Roger Leigh <mailto:[email protected]>`_
 * `Rolf Eike Beer <mailto:[email protected]>`_
 * `Roman Donchenko <mailto:[email protected]>`_