chore: Drop support for Rails 6.1 and older (#1678)

On this commit we're removing support for Rails 6.1 and older versions.

Author: matsales28

.github/workflows/ci.yml

@@ -36,15 +36,11 @@ jobs:
           - rails_7_2
           - rails_7_1
           - rails_7_0
-          - rails_6_1
         adapter:
           - sqlite3
           - postgresql
         exclude:
           - { ruby: 3.4.5, appraisal: rails_7_0 }
-          - { ruby: 3.4.5, appraisal: rails_6_1 }
-          - { ruby: 3.3.9, appraisal: rails_6_1 }
-          - { ruby: 3.2.9, appraisal: rails_6_1 }
           - { ruby: 3.0.7, appraisal: rails_7_0 }
           - { ruby: 3.0.7, appraisal: rails_7_1 }
           - { ruby: 3.0.7, appraisal: rails_7_2 }