Merge pull request #10892 from haskell/dep-ext-docs

Fix docs: extensions field was deprecated in Cabal 1.10, not 1.12

Author: mergify[bot]

Diff for: doc/cabal-package-description-file.rst

@@ -1634,7 +1634,7 @@ system-dependent values for these fields.
     Specifies a language standard used by some (but not necessarily all) modules.
 
 .. pkg-field:: extensions: identifier list
-   :deprecated: 1.12
+   :deprecated: 1.10
    :removed: 3.0
 
    Deprecated in favor of :pkg-field:`default-extensions`.