sl_vm: update docs about requirements (#10282)

* sl_vm: update docs about requirements

* Update plugins/modules/sl_vm.py

Author: russoz

plugins/modules/sl_vm.py

@@ -173,8 +173,16 @@
     type: int
 requirements:
   - softlayer >= 4.1.1
+notes:
+  - If using Python 2.7, you must install C(softlayer-python<=5.7.2).
+  - If using Python 3.6, you must install C(softlayer-python<=6.0.0).
+  - The C(softlayer-python) library, at version 6.2.6 (from Jan 2025), only supports Python version 3.8, 3.9 and 3.10.
 author:
   - Matt Colton (@mcltn)
+seealso:
+  - name: SoftLayer API Python Client
+    description: The SoftLayer API Python Client is required for this module.
+    link: https://github.com/SoftLayer/softlayer-python
 """
 
 EXAMPLES = r"""