[ruby/open-uri] Bump version to 0.3.0

https://github.com/ruby/open-uri/commit/783892ebb0

lib/open-uri.gemspec

@@ -1,6 +1,6 @@
 Gem::Specification.new do |spec|
   spec.name          = "open-uri"
-  spec.version       = "0.2.0"
+  spec.version       = "0.3.0"
   spec.authors       = ["Tanaka Akira"]
   spec.email         = ["akr@fsij.org"]