Bump rails_admin from 2.0.2 to 2.1.1

Bumps [rails_admin](https://github.com/sferik/rails_admin) from 2.0.2 to 2.1.1.
- [Release notes](https://github.com/sferik/rails_admin/releases)
- [Changelog](https://github.com/sferik/rails_admin/blob/master/CHANGELOG.md)
- [Commits](railsadminteam/rails_admin@v2.0.2...v2.1.1)

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile.lock

@@ -213,8 +213,8 @@ GEM
     faraday_middleware (0.14.0)
       faraday (>= 0.7.4, < 1.0)
     fast_blank (1.0.0)
-    fastimage (2.2.2)
-    ffi (1.14.2)
+    fastimage (2.2.3)
+    ffi (1.15.0)
     ffi-compiler (1.0.1)
       ffi (>= 1.0.0)
       rake
@@ -288,7 +288,7 @@ GEM
       guard (~> 2.1)
       guard-compat (~> 1.1)
       rspec (>= 2.99.0, < 4.0)
-    haml (5.1.2)
+    haml (5.2.1)
       temple (>= 0.8.0)
       tilt
     hashdiff (1.0.1)
@@ -418,7 +418,7 @@ GEM
     net-http-digest_auth (1.4.1)
     net-http-persistent (4.0.1)
       connection_pool (~> 2.2)
-    nio4r (2.5.5)
+    nio4r (2.5.7)
     nokogiri (1.11.1)
       mini_portile2 (~> 2.5.0)
       racc (~> 1.4)
@@ -509,7 +509,7 @@ GEM
     rails_12factor (0.0.3)
       rails_serve_static_assets
       rails_stdout_logging
-    rails_admin (2.0.2)
+    rails_admin (2.1.1)
       activemodel-serializers-xml (>= 1.0)
       builder (~> 3.1)
       haml (>= 4.0, < 6)