fix: File.exists() is deprecated and removed in Ruby 3.2.0

Signed-off-by: Rophy Tsai <rophy@users.noreply.github.com>

Author: rophy

lib/fluent/plugin/in_sql.rb

@@ -282,7 +282,7 @@ def initialize(path)
         require 'yaml'
 
         @path = path
-        if File.exists?(@path)
+        if File.exist?(@path)
           @data = YAML.load_file(@path)
           if @data == false || @data == []
             # this happens if an users created an empty file accidentally