Remove workarounds for destructuring single-element hashes

Library/Homebrew/compilers.rb

@@ -32,7 +32,7 @@ class CompilerFailure
   def self.create(spec, &block)
     # Non-Apple compilers are in the format fails_with compiler => version
     if spec.is_a?(Hash)
-      _, major_version = spec.each { |e| break e }
+      _, major_version = spec.first
       name = "gcc-#{major_version}"
       # so fails_with :gcc => '4.8' simply marks all 4.8 releases incompatible
       version = "#{major_version}.999"

Library/Homebrew/dependency_collector.rb

@@ -57,20 +57,12 @@ class DependencyCollector
   end
 
   def build(spec)
-    spec, tags = case spec
-                 when Hash then destructure_spec_hash(spec)
-                 else spec
-                 end
-
+    spec, tags = Hash === spec ? spec.first : spec
     parse_spec(spec, Array(tags))
   end
 
   private
 
-  def destructure_spec_hash(spec)
-    spec.each { |o| return o }
-  end
-
   def parse_spec(spec, tags)
     case spec
     when String