Re-enable strict mode in docs vlidation. Bump mkdocs-material version (#3073)

- Re-enable strict mode in the verify docs command now that the latest version of mkdocs-material is available and supports the new Google Analytics layout
- Amend mkdocs config to use the new Google Analytics layout
- Bump to use latest 1.2 version of mkdocs

Note - current issue https://github.com/mkdocs/mkdocs/issues/2457 stops live reload from work in mkdocs 1.2 so developers will need to amend the mkdocs.yml
to pin mkdocs to version 1.1.2

Signed-off-by: Steve Richards <srichards@mirantis.com>

mkdocs.yml

@@ -7,9 +7,6 @@ repo_name: GitHub
 repo_url: https://github.com/lensapp/lens
 copyright: Copyright &copy; 2021 <a href="https://mirantis.com/">Mirantis Inc.</a> - All rights reserved.
 edit_uri: ""
-google_analytics:
-  - UA-159377374-2
-  - auto
 nav:
   - Overview: README.md
   - Getting Started:
@@ -87,3 +84,6 @@ extra:
       name: Lens Website
   version:
     method: mike
+  analytics:
+    provider: google
+    property: UA-159377374-2