Remove cabal-doctest-1.0.6.cabal; there is a patch

patches/cabal-doctest-1.0.6.cabal

-name:                cabal-doctest
-version:             1.0.6
-synopsis:            A Setup.hs helper for doctests running
-description:
-  Currently (beginning of 2017), there isn't @cabal doctest@
-  command. Yet, to properly work doctest needs plenty of configuration.
-  This library provides the common bits for writing custom Setup.hs
-
-  See <https://github.com/haskell/cabal/issues/2327 Cabal/2327> for the progress
-  of @cabal doctest@, i.e. whether this library is obsolete.
-
-homepage:            https://github.com/phadej/cabal-doctest
-license:             BSD3
-license-file:        LICENSE
-author:              Oleg Grenrus <oleg.grenrus@iki.fi>
-maintainer:          Oleg Grenrus <oleg.grenrus@iki.fi>
-copyright:           (c) 2017 Oleg Grenrus
-category:            Distribution
-build-type:          Simple
-cabal-version:       >=1.10
-extra-source-files:  ChangeLog.md README.md
-tested-with:
-  GHC==7.0.4,
-  GHC==7.2.2,
-  GHC==7.4.2,
-  GHC==7.6.3,
-  GHC==7.8.4,
-  GHC==7.10.3,
-  GHC==8.0.2,
-  GHC==8.2.2,
-  GHC==8.4.3,
-  GHC==8.6.1
-
-source-repository head
-  type:     git
-  location: https://github.com/phadej/cabal-doctest
-
-library
-  exposed-modules:     Distribution.Extra.Doctest
-  other-modules:
-  other-extensions:
-  build-depends:
-    base >=4.3 && <4.13,
-    Cabal >= 1.10 && <2.5,
-    filepath,
-    directory
-  hs-source-dirs:      src
-  default-language:    Haskell2010