ci test: drop support for Redmine 5.0 (#183)

It's because Redmine 5.0 has already reached EOL.

ref: https://www.redmine.org/news/156

Author: otegami

.github/workflows/test.yml

@@ -14,12 +14,6 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - redmine-version: "5.0"
-            ruby-version: "3.1"
-            rdbms: "MySQL"
-          - redmine-version: "5.0"
-            ruby-version: "3.1"
-            rdbms: "PostgreSQL"
           - redmine-version: "5.1"
             ruby-version: "3.2"
             rdbms: "MySQL"

README.md

@@ -269,7 +269,7 @@ Clone source codes. This is required only once.
 ```console
 $ git clone https://github.com/redmine/redmine.git
 $ cd redmine
-$ git checkout 5.0-stable # or something
+$ git checkout 6.1-stable # or something
 $ git clone [email protected]:${YOUR_FORK}/redmine_full_text_search.git plugins/full_text_search
 ```
 
@@ -281,10 +281,10 @@ Choose suitable database configuration:
 $ ln -fs ../plugins/full_text_search/config/database.yml.example.${REDMINE_VERSION}.${RDBMS} config/database.yml
 ```
 
-Here is an example to use Redmine 5.0 and MySQL:
+Here is an example to use Redmine 6.1 and MySQL:
 
 ```console
-$ ln -fs ../plugins/full_text_search/config/database.yml.example.5.0.mysql config/database.yml
+$ ln -fs ../plugins/full_text_search/config/database.yml.example.6.1.mysql config/database.yml
 ```
 
 Run RDBMS.

app/models/fts_query_expansion.rb

@@ -1,10 +1,5 @@
 class FtsQueryExpansion < ApplicationRecord
-  if respond_to?(:connection_db_config)
-    adapter = connection_db_config.adapter
-  else
-    adapter = connection_config[:adapter]
-  end
-  case adapter
+  case connection_db_config.adapter
   when "postgresql"
     include FullTextSearch::Pgroonga
   when "mysql2"

app/models/full_text_search/tag.rb

@@ -3,12 +3,7 @@ class Tag < ApplicationRecord
     self.table_name = :fts_tags
     belongs_to :type, class_name: "FullTextSearch::TagType"
 
-    if respond_to?(:connection_db_config)
-      adapter = connection_db_config.adapter
-    else
-      adapter = connection_config[:adapter]
-    end
-    case adapter
+    case connection_db_config.adapter
     when "postgresql"
       include Pgroonga
     when "mysql2"

app/models/full_text_search/target.rb

@@ -2,12 +2,7 @@ module FullTextSearch
   class Target < ApplicationRecord
     self.table_name = :fts_targets
 
-    if respond_to?(:connection_db_config)
-      adapter = connection_db_config.adapter
-    else
-      adapter = connection_config[:adapter]
-    end
-    case adapter
+    case connection_db_config.adapter
     when "postgresql"
       include Pgroonga
     when "mysql2"