servant-multipart: allow lens 5.2 (#64)

Tested in conjunction with haskell-servant/servant#1607

servant-multipart/servant-multipart.cabal

@@ -36,7 +36,7 @@ library
   -- other dependencies
   build-depends:
       servant-multipart-api == 0.12.*
-    , lens                >=4.17     && <5.2
+    , lens                >=4.17     && <5.3
     , resourcet           >=1.2.2    && <1.3
     , servant             >=0.16     && <0.20
     , servant-docs        >=0.10     && <0.20