Upgrade to sbt 1.5.8.

sjrd · sjrd · commit abc306979935 · 2021-12-22T11:31:53.000+01:00
It contains upgrades to newer versions of log4j, addressing recent
security issues. It is unclear that these issues are a security
concern for this particular repo, but there is also no point in
*not* upgrading.
diff --git a/project/build.properties b/project/build.properties
@@ -1 +1 @@
-sbt.version=1.5.4
+sbt.version=1.5.8
diff --git a/sbt-plugin/src/sbt-test/scala3/basic/project/build.properties b/sbt-plugin/src/sbt-test/scala3/basic/project/build.properties
@@ -1 +1 @@
-sbt.version=1.5.4
+sbt.version=1.5.8
diff --git a/sbt-plugin/src/sbt-test/scala3/junit/project/build.properties b/sbt-plugin/src/sbt-test/scala3/junit/project/build.properties
@@ -1 +1 @@
-sbt.version=1.5.4
+sbt.version=1.5.8
