Update target version to 11

Author: takezoe

.github/workflows/build.yml

@@ -8,7 +8,7 @@ jobs:
     timeout-minutes: 20
     strategy:
       matrix:
-        java: [8, 11]
+        java: [11]
     steps:
     - uses: actions/checkout@v3
     - name: Cache

build.sbt

@@ -5,6 +5,6 @@ scalaVersion := "2.13.10"
 gitbucketVersion := "4.39.0"
 
 scalacOptions := Seq("-deprecation", "-feature", "-language:postfixOps")
-Compile / javacOptions ++= Seq("-target", "8", "-source", "8")
+Compile / javacOptions ++= Seq("-target", "11", "-source", "11")
 
 useJCenter := true