Drop GHC 8.4 and 8.6 support

Author: snoyberg

.github/workflows/unit-tests.yml

@@ -46,14 +46,6 @@ jobs:
       fail-fast: false
       matrix:
         include:
-        - os: ubuntu-latest
-          stack-yaml: stack-ghc-84.yaml
-          extra-suffix: ""
-          stack-args: ""
-        - os: ubuntu-latest
-          stack-yaml: stack-ghc-86.yaml
-          extra-suffix: ""
-          stack-args: ""
         - os: ubuntu-latest
           stack-yaml: stack-ghc-88.yaml
           extra-suffix: ""

package.yaml

@@ -22,7 +22,7 @@ github: commercialhaskell/stack
 homepage: http://haskellstack.org
 custom-setup:
   dependencies:
-  - base >=4.10 && < 5
+  - base >=4.13 && < 5
   - Cabal
   - filepath
 extra-source-files:

stack-ghc-84.yaml

@@ -4,7 +4,7 @@ cabal-version: 2.0
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: a7991e56b8dd0142add4bc2a07936396678427485a932aab9ca6c721d036b3a3
+-- hash: 08598058e5bbf079a51f3a86109460e78eca2b1157c655b140096979963c432e
 
 name:           stack
 version:        2.7.0.2
@@ -74,7 +74,7 @@ source-repository head
 custom-setup
   setup-depends:
       Cabal
-    , base >=4.10 && <5
+    , base >=4.13 && <5
     , filepath
 
 flag developer-mode