Update sbt, scripted-plugin to 1.12.6 in series/0.26

http4s-steward[bot] · http4s-steward[bot] · commit 45aa1ea50bcd · 2026-03-16T02:34:54.000Z
diff --git a/project/build.properties b/project/build.properties
@@ -1 +1 @@
-sbt.version=1.12.5
+sbt.version=1.12.6
