Update sbt-lift-build plugin

[lvitaly]

After bumping SBT version #2000, two SBT-related issues, #1998 and #1999, will be fixed. But there is still a place for improvement. And it would be great to update the sbt-lift-build plugin with lift/sbt-lift-build#3. It will help to remove warnings from the console.

[info] welcome to sbt 1.6.2 (Azul Systems, Inc. Java 11.0.14)
[info] loading global plugins from /Users/vl/.sbt/1.0/plugins
[info] loading settings for project root from plugins.sbt ...
Cloning into '/Users/vl/.sbt/1.0/staging/a6a77c219d2001172bee/sbt-lift-build'...
[info] loading project definition from /Users/vl/.sbt/1.0/staging/a6a77c219d2001172bee/sbt-lift-build/project
/Users/vl/.sbt/1.0/staging/a6a77c219d2001172bee/sbt-lift-build/build.sbt:13: warning: method in in trait ScopingSetting is deprecated (since 1.5.0): `in` is deprecated; migrate to slash syntax - https://www.scala-sbt.org/1.x/docs/Migrating-from-sbt-013x.html#slash
scalacOptions in Compile += Opts.compile.deprecation
              ^
/Users/vl/.sbt/1.0/staging/a6a77c219d2001172bee/sbt-lift-build/build.sbt:15: warning: method in in trait ScopingSetting is deprecated (since 1.5.0): `in` is deprecated; migrate to slash syntax - https://www.scala-sbt.org/1.x/docs/Migrating-from-sbt-013x.html#slash
publishArtifact in (Compile, packageDoc) := false
                ^
/Users/vl/.sbt/1.0/staging/a6a77c219d2001172bee/sbt-lift-build/build.sbt:17: warning: method in in trait ScopingSetting is deprecated (since 1.5.0): `in` is deprecated; migrate to slash syntax - https://www.scala-sbt.org/1.x/docs/Migrating-from-sbt-013x.html#slash
publishArtifact in (Compile, packageSrc) := false
                ^
[info] loading settings for project sbt-lift-build from build.sbt ...
[info] loading project definition from /Users/vl/dev/git/oss/lift-framework/project
[info] compiling 1 Scala source to /Users/vl/.sbt/1.0/staging/a6a77c219d2001172bee/sbt-lift-build/target/scala-2.12/sbt-1.0/classes ...
[warn] /Users/vl/.sbt/1.0/staging/a6a77c219d2001172bee/sbt-lift-build/src/main/scala/LiftBuild.scala:89:61: lazy value formatEnabledInEnv in object ConsoleAppender is deprecated (since 1.4.0): Use Terminal.isAnsiSupported or Terminal.isColorEnabled
[warn]           Seq(arr, txt, abt) map { l => if (ConsoleAppender.formatEnabledInEnv) colorize(l._1)(l._2, RESET) else colorize(l._1)() }
[warn]                                                             ^
[warn] one warning found
[info] loading settings for project lift-framework from build.sbt ...
[info] resolving key references (14799 settings) ...
   ___,__      _     _   __  _
  |  / \  \   | |   (_)/  _|| |_    lift-framework
  |  | |  |   | |__ | ||  _||  _|   3.6.0-SNAPSHOT for Scala 2.12.15
   \__\_\_.   |____||_||_|   \__|

[info] set current project to lift-framework (in build file:/Users/vl/dev/git/oss/lift-framework/)
[info] sbt server started at local:///Users/vl/.sbt/1.0/server/698fac976289124337e4/sock
[info] started sbt server
sbt:lift-framework>