Fix gettext bug on Contract's Code page

apps/block_scout_web/lib/block_scout_web/templates/address_contract/index.html.eex

@@ -24,7 +24,7 @@
           </dl>
           <dl class="row">
             <dt class="col-sm-4 col-md-2 text-muted"><%= gettext "Optimization enabled" %></dt>
-            <dd class="col-sm-8 col-md-10"><%= gettext("%{}", @address.smart_contract.optimization) %></dd>
+            <dd class="col-sm-8 col-md-10"><%= format_optimization_text(@address.smart_contract.optimization) %></dd>
           </dl>
           <dl class="row">
             <dt class="col-sm-4 col-md-2 text-muted"><%= gettext "Compiler version" %></dt>

apps/block_scout_web/lib/block_scout_web/views/address_contract_view.ex

@@ -2,4 +2,16 @@ defmodule BlockScoutWeb.AddressContractView do
   use BlockScoutWeb, :view
 
   def format_smart_contract_abi(abi), do: Poison.encode!(abi, pretty: false)
+
+  @doc """
+  Returns the correct format for the optimization text.
+
+    iex> BlockScoutWeb.AddressContractView.format_optimization_text(true)
+    "true"
+
+    iex> BlockScoutWeb.AddressContractView.format_optimization_text(false)
+    "false"
+  """
+  def format_optimization_text(true), do: gettext("true")
+  def format_optimization_text(false), do: gettext("false")
 end

apps/block_scout_web/test/block_scout_web/views/address_contract_view_test.exs

@@ -0,0 +1,17 @@
+defmodule BlockScoutWeb.AddressContractViewTest do
+  use BlockScoutWeb.ConnCase, async: true
+
+  alias BlockScoutWeb.AddressContractView
+
+  doctest BlockScoutWeb.AddressContractView
+
+  describe "format_optimization_text/1" do
+    test "returns \"true\" for the boolean true" do
+      assert AddressContractView.format_optimization_text(true) == "true"
+    end
+
+    test "returns \"false\" for the boolean false" do
+      assert AddressContractView.format_optimization_text(false) == "false"
+    end
+  end
+end