Update scala-library to 2.12.15

Author: scala-steward

.github/workflows/ci.yml

@@ -26,7 +26,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        scala: [2.11.12, 2.12.14, 2.13.6, 3.0.2]
+        scala: [2.11.12, 2.12.15, 2.13.6, 3.0.2]
         java: [temurin@11]
         ci: [ciNode, ciFirefox, ciChrome, ciJSDOMNodeJS]
     runs-on: ${{ matrix.os }}