Drop surro-gate CFLAGS after v1.0.6

Drop the bundle config cflags documentation now that v1.0.6 fixes the
pointer casting.

Author: agrare

developer_setup.md

@@ -222,18 +222,6 @@ bin/setup
 
 - macOS requires platform specific Gems. Run `bundle config specific_platform true` before running `bin/setup`.
 
-- The `surro-gate` gem contains C code which generates errors on some compilers.
-
-  You can add build flags to your bundler config:
-  ```
-  bundle config set build.surro-gate --with-cflags=\"-Wno-error=incompatible-pointer-types\"
-  ```
-
-  Or use `gem install`:
-  ```
-  gem install surro-gate -- --with-cflags="-Wno-error=incompatible-pointer-types"
-  ```
-
 - If you've run PostgreSQL in a container, be sure to export the `DATABASE_URL` variable to connect to the container over TCP instead of a UNIX file socket.
 
   ```bash