README: update references to internal docs

These documents are no longer HTML files, so the internal reference
should be updated.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4630>
diff --git a/README.rst b/README.rst
index 9e44d78..c78c0df 100644
--- a/README.rst
+++ b/README.rst
@@ -12,9 +12,9 @@
 Build & install
 ---------------
 
-You can find more information in our documentation (`docs/install.html
+You can find more information in our documentation (`docs/install.rst
 <https://mesa3d.org/install.html>`_), but the recommended way is to use
-Meson (`docs/meson.html <https://mesa3d.org/meson.html>`_):
+Meson (`docs/meson.rst <https://mesa3d.org/meson.html>`_):
 
 .. code-block:: sh
 
@@ -46,14 +46,14 @@
 -----------
 
 If you think something isn't working properly, please file a bug report
-(`docs/bugs.html <https://mesa3d.org/bugs.html>`_).
+(`docs/bugs.rst <https://mesa3d.org/bugs.html>`_).
 
 
 Contributing
 ------------
 
 Contributions are welcome, and step-by-step instructions can be found in our
-documentation (`docs/submittingpatches.html
+documentation (`docs/submittingpatches.rst
 <https://mesa3d.org/submittingpatches.html>`_).
 
 Note that Mesa uses gitlab for patches submission, review and discussions.