Revert of [iOS] Disable NSAssert and GTMDevAssert on release builds.

build/config/BUILD.gn

Index: build/config/BUILD.gn
diff --git a/build/config/BUILD.gn b/build/config/BUILD.gn
index 09cb18f44434d3ded8b00e5911b57fa69b0196d0..80427f26a087b631031ad3a45bd017547898a4a9 100644
--- a/build/config/BUILD.gn
+++ b/build/config/BUILD.gn
@@ -220,12 +220,6 @@
       # 1 for all .nexes.
       defines += [ "DYNAMIC_ANNOTATIONS_ENABLED=0" ]
     }
-  }
-
-  if (is_ios) {
-    # Disable NSAssert and GTMDevAssert (from Google Toolbox for Mac). This
-    # follows XCode's default behavior for Release builds.
-    defines += [ "NS_BLOCK_ASSERTIONS=1" ]
   }
 }