Typecast invalid BigDecimal to 0.0 regardless of Ruby version

Fixes a CI failure on Ruby 2.0.0, where a newer BigDecimal gem
was used.

Author: jeremyevans

lib/sequel/extensions/looser_typecasting.rb

@@ -37,18 +37,11 @@ def typecast_value_string(value)
       value.to_s
     end
 
-    if RUBY_VERSION >= '2.4'
-      def _typecast_value_string_to_decimal(value)
-        BigDecimal(value)
-      rescue
-        BigDecimal('0.0')
-      end
-    else
-      # :nocov:
-      def _typecast_value_string_to_decimal(value)
-        BigDecimal(value)
-      end
-      # :nocov:
+    # Typecast invalid BigDecimal to 0.0.
+    def _typecast_value_string_to_decimal(value)
+      BigDecimal(value)
+    rescue
+      BigDecimal('0.0')
     end
   end