GEODE-10401: Replace 1.15.0 with 1.15.1 as old version (#7868)

Replace 1.15.0 with 1.15.1 in old versions and set as default Benchmarks baseline on develop
to enable rolling upgrade tests from 1.15.1

The serialization version has not changed between 1.15.0 and 1.15.1,
so there should be no need to keep both

ci/pipelines/shared/jinja.variables.yml

@@ -17,7 +17,7 @@
 
 benchmarks:
   baseline_branch_default: ''
-  baseline_version_default: '1.14.4'
+  baseline_version_default: '1.15.1'
   benchmark_branch: ((geode-build-branch))
   flavors:
   - title: 'base'