fix(pg): update versions to be tested (includes drop support for pg 1…

….2) (#1108)

* include pg 1.4 in Appraisals

* drop pg-1.2 from tests

* pg 1.2.x does not work under Ruby >= 3.0.
* We currently support and test only Ruby >= 3.0.

instrumentation/pg/Appraisals

@@ -1,15 +1,13 @@
 # frozen_string_literal: true
 
-# 1.2.3 appears to be the most popular version at RubyGems.org
-appraise 'pg-1.2' do
-  gem 'pg', '~> 1.2.3'
-end
-
-# 1.3.0 significantly changed connecting and the handling of connection strings
 appraise 'pg-1.3' do
   gem 'pg', '~> 1.3.5'
 end
 
+appraise 'pg-1.4' do
+  gem 'pg', '~> 1.4.5'
+end
+
 appraise 'pg-latest' do
   gem 'pg'
 end