Drop ghc-8.8 support

Problem: supporting ghc-8.8 forces us to have some conditionals
in the .cabal file. Not a big deal, but still some overhead.
Nowadays this compiler version is rather old, and since we claim
to always support 3 versions (as a minimum) it's safe to drop
the oldest supported one.

Solution: remove it from CI config and tested-with, remove
related conditionals.

.github/workflows/ci.yml

@@ -35,7 +35,6 @@ jobs:
         # If you update this list of supported compiler versions,
         # make sure to update the `tested-with` section of `universum.cabal`.
         ghc:
-          - "8.8.4"
           - "8.10.7"
           - "9.0.2"
           - "9.2.8"
@@ -46,16 +45,12 @@ jobs:
             ghc: 9.2.8
           - os: macOS-latest
             ghc: 9.0.2
-          - os: macOS-latest
-            ghc: 8.8.4
           - os: macOS-latest
             ghc: 8.10.7
           - os: windows-latest
             ghc: 9.2.8
           - os: windows-latest
             ghc: 9.0.2
-          - os: windows-latest
-            ghc: 8.8.4
           - os: windows-latest
             ghc: 8.10.7
 

universum.cabal

@@ -13,8 +13,7 @@ category:            Prelude
 stability:           stable
 build-type:          Simple
 bug-reports:         https://github.com/serokell/universum/issues
-tested-with:         GHC == 8.8.4
-                   , GHC == 8.10.7
+tested-with:         GHC == 8.10.7
                    , GHC == 9.0.2
                    , GHC == 9.2.8
                    , GHC == 9.4.5
@@ -40,8 +39,7 @@ common common-options
                        -Wno-missing-local-signatures
                        -Wno-monomorphism-restriction
                        -Wno-implicit-prelude
-  if impl(ghc >= 8.10.1)
-    ghc-options:       -Wno-prepositive-qualified-module
+                       -Wno-prepositive-qualified-module
                        -Wno-inferred-safe-imports
   if impl(ghc >= 9.2.0)
     ghc-options:         -Wno-missing-kind-signatures
@@ -140,9 +138,7 @@ test-suite universum-test
   build-tool-depends:
       tasty-discover:tasty-discover
 
-  if impl(ghc >= 8.10.1)
-    ghc-options:         -Wno-missing-safe-haskell-mode
-
+  ghc-options:         -Wno-missing-safe-haskell-mode
   ghc-options:         -threaded
 
 test-suite universum-doctest
@@ -157,15 +153,13 @@ test-suite universum-doctest
   build-depends:       doctest
                      , Glob
 
-  if impl(ghc >= 8.10.1)
-    ghc-options:         -Wno-missing-safe-haskell-mode
+  ghc-options:         -Wno-missing-safe-haskell-mode
+  ghc-options:         -threaded
   -- https://github.com/sol/doctest/issues/327
   -- TODO: re-enable when the issue is resolved
   if impl(ghc >= 9.0.0)
     buildable: False
 
-  ghc-options:         -threaded
-
 benchmark universum-benchmark
   import:              common-options
   type:                exitcode-stdio-1.0
@@ -179,8 +173,7 @@ benchmark universum-benchmark
                      , text
                      , unordered-containers
 
-  if impl(ghc >= 8.10.1)
-    ghc-options:         -Wno-missing-safe-haskell-mode
+  ghc-options:         -Wno-missing-safe-haskell-mode
 
   default-extensions:  NoImplicitPrelude
                        ScopedTypeVariables