Drop '--allow-newer=Cabal' from various places.

See haskell/hackage-security#151.

.travis.yml

@@ -72,7 +72,7 @@ script:
  - cp Setup.hs ./dist/setup/setup.hs
  - ghc --make -odir ./dist/setup -hidir ./dist/setup -i -i. ./dist/setup/setup.hs -o ./dist/setup/setup -Wall -Werror -threaded  # the command cabal-install would use to build setup
 
- - cabal install --only-dependencies --enable-tests --enable-benchmarks --allow-newer=Cabal
+ - cabal install --only-dependencies --enable-tests --enable-benchmarks
  - ./dist/setup/setup configure --user --ghc-option=-Werror --enable-tests --enable-benchmarks -v2 # -v2 provides useful information for debugging
  - ./dist/setup/setup build
  - ./dist/setup/setup haddock # see https://github.com/haskell/cabal/issues/2198

HACKING.md

@@ -122,7 +122,7 @@ identical; only the first two steps are different:
     ~~~~
     cabal sandbox init
     cabal sandbox add-source ../Cabal/
-    cabal install --only-dependencies --enable-tests --allow-newer=Cabal
+    cabal install --only-dependencies --enable-tests
     ~~~~
 
 (In addition, the absolute sandbox path will be slightly different

appveyor.yml

@@ -21,7 +21,7 @@ build_script:
   - Setup install
   - cd ..\cabal-install
   - ghc --make -threaded -i -i. Setup.hs -Wall -Werror
-  - echo "" | ..\cabal install --only-dependencies --enable-tests --force-reinstalls --allow-newer=Cabal
+  - echo "" | ..\cabal install --only-dependencies --enable-tests --force-reinstalls
   - ..\cabal configure --user --ghc-option=-Werror --enable-tests
   - ..\cabal build
   - ..\cabal test unit-tests --show-details=streaming --test-option=--pattern=!FileMonitor