allow testing with newer Nim version

stefantalpalaru · stefantalpalaru · commit c4037a7920b9 · 2021-11-19T00:44:06.000+01:00
diff --git a/eth.nimble b/eth.nimble
@@ -4,7 +4,7 @@ description   = "Ethereum Common library"
 license       = "MIT"
 skipDirs      = @["tests"]
 
-requires "nim >= 1.2.0 & <= 1.2.14",
+requires "nim >= 1.2.0",
          "nimcrypto",
          "stint",
          "secp256k1",
