Fix typo [ci skip]

Closes Homebrew/homebrew#48008.

Signed-off-by: Baptiste Fontaine <batifon@yahoo.fr>

Library/Homebrew/requirement.rb

@@ -69,7 +69,7 @@ class Requirement
   end
 
   # Overriding #modify_build_environment is deprecated.
-  # Pass a block to the the env DSL method instead.
+  # Pass a block to the env DSL method instead.
   # Note: #satisfied? should be called before invoking this method
   # as the env modifications may depend on its side effects.
   def modify_build_environment