Travis: Fully enable GHC 8.6

.travis.yml

@@ -2,7 +2,7 @@
 #
 #   runghc make_travis_yml_2.hs '-o' '.travis.yml' '--ghc-head' '--irc-channel=irc.freenode.org#haskell-lens' '--no-no-tests-no-bench' '--no-unconstrained' '--env=7.6.3:HADDOCK=false' '--env=7.8.4:NOINSTALLEDCONSTRAINTS=true' 'cabal.project'
 #
-# For more information, see https://github.com/hvr/multi-ghc-travis
+# For more information, see https://github.com/haskell-CI/haskell-ci
 #
 language: c
 sudo: false
@@ -37,7 +37,7 @@ before_cache:
 matrix:
   include:
     - compiler: "ghc-8.6.1"
-      env: GHCHEAD=true
+    # env: TEST=--disable-tests BENCH=--disable-benchmarks
       addons: {apt: {packages: [ghc-ppa-tools,cabal-install-head,ghc-8.6.1], sources: [hvr-ghc]}}
     - compiler: "ghc-8.4.3"
     # env: TEST=--disable-tests BENCH=--disable-benchmarks
@@ -72,7 +72,6 @@ matrix:
 
   allow_failures:
     - compiler: "ghc-head"
-    - compiler: "ghc-8.6.1"
 
 before_install:
   - HC=${CC}