DEV: update mini_sql to remove deprecation

DEV: update mini_sql to remove deprecation

The only reason this was done was to remove this deprecation when running tests.

/home/sam/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/mini_sql-0.1.10/lib/mini_sql/coders.rb:5: warning: BigDecimal.new is deprecated; use BigDecimal() method instead.
diff --git a/Gemfile.lock b/Gemfile.lock
index 49c2292..35768be 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -205,7 +205,7 @@ GEM
       libv8 (>= 6.3)
     mini_scheduler (0.9.1)
       sidekiq
-    mini_sql (0.1.10)
+    mini_sql (0.2.1)
     mini_suffix (0.3.0)
       ffi (~> 1.9)
     minitest (5.11.3)

GitHub sha: e8e61535

Revert "DEV: update mini_sql to remove deprecation"