Formally drop support for Python 3.5

This MR formally drops support for Python 3.5 and updates the docs to not include references to the support Python versions.

docs/index.rst

@@ -15,43 +15,35 @@ Installation
 
           $ python -m pip install gwdatafind
 
-      Supported python versions: 2.7, 3.4+.
-
    .. tab:: Conda
 
       .. code-block:: bash
 
           $ conda install -c conda-forge gwdatafind
 
-      Supported python versions: 2.7, 3.5+.
-
    .. tab:: Debian Linux
 
       .. code-block:: bash
 
-          $ apt-get install python3-gwdatafind
+          $ apt-get install gwdatafind
 
-      Supported python versions: 2.7, 3.4 (Jessie), 3.5 (Stretch), 3.6 (Buster),
-      `click here for instructions on how to add the required debian repositories
-      <https://wiki.ligo.org/Computing/Debian>`__.
+      See the IGWN Computing Guide software repositories entry for
+      `Debian <https://computing.docs.ligo.org/guide/software/debian/>`__
+      for instructions on how to configure the required
+      IGWN Debian repositories.
 
    .. tab:: Scientific Linux
 
       .. code-block:: bash
 
-          $ yum install python-gwdatafind
-
-      Supported python versions: 2.7, `click here for instructions on how to add
-      the required yum repositories
-      <https://wiki.ligo.org/Computing/ScientificLinux7>`__.
-
-   .. tab:: Macports
-
-      .. code-block:: bash
-
-          $ port install py37-gwdatafind
+          $ yum install gwdatafind
 
-      Supported python versions: 2.7, 3.6, 3.7.
+      See the IGWN Computing Guide software repositories entries for
+      `Scientific Linux 7
+      <https://computing.docs.ligo.org/guide/software/sl7/>`__
+      or
+      `Rocky Linux 8 <https://computing.docs.ligo.org/guide/software/rl8/>`__
+      for instructions on how to configure the required IGWN Yum repositories.
 
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