Drop OTP 22 & 23 in test matrix

ubuntu-latest now points to 22.04, and erlef/setup-beam is only
compatible with OTP 24 & 25.

See https://github.com/erlef/setup-beam#compatibility-between-operating-system-and-erlangotp

(Using ubuntu-20.04 explicitly let some OTP/Elixir combinations fail due
to a not available GLIBC_2.33 version.)

in order to fix compatibility issues of the OTP & OS version
with /erlef/setup-beam.

.github/workflows/tests.yml

@@ -20,11 +20,9 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        otp: [22.2, 23.3, 24.3, 25.1]
-        elixir: [1.11.4, 1.12.3, 1.13.4, 1.14.0]
+        otp: [24.3, 25.1]
+        elixir: [1.11.4, 1.12.3, 1.13.4, 1.14.2]
         exclude:
-          - otp: 22.2
-            elixir: 1.14.0
           - otp: 25.1
             elixir: 1.11.4
           - otp: 25.1