Upgrade to sbt 1.5.5.

Author: sjrd

.github/workflows/ci.yml

@@ -21,5 +21,9 @@ jobs:
       - uses: coursier/cache-action@v5
       - name: Build
         run: sbt "++${{ matrix.scalaversion }}" scalajs-stubs/publishLocal
+
+      # MiMa is not run for the Scala 2.10.x artifact because there is no
+      # version of sbt-mima that works with sbt 1.5.x and for Scala 2.10.x.
       - name: MiMa
+        if: matrix.scalaversion != '2.10.7'
         run: sbt "++${{ matrix.scalaversion }}" scalajs-stubs/mimaReportBinaryIssues

project/build.properties

@@ -1 +1 @@
-sbt.version=1.2.8
+sbt.version=1.5.5

project/plugins.sbt

@@ -1 +1 @@
-addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "0.2.0")
+addSbtPlugin("com.typesafe" % "sbt-mima-plugin" % "0.8.1")