chore: Bump Scalameta to 4.8.12 #11525

Job	Run time
windows-latest jdk-17 unit tests 1 / 2	30m 17s
windows-latest jdk-17 unit tests 2 / 2	21m 30s
Gradle MacOS integration	11m 30s
macOS-latest jdk-17 unit tests 1 / 2	22m 20s
Sbt integration	54m 3s
macOS-latest jdk-17 unit tests 2 / 2	23m 32s
Maven integration	13m 36s
ubuntu-latest jdk-17 unit tests 1 / 2	18m 16s
Gradle integration	9m 32s
ubuntu-latest jdk-17 unit tests 2 / 2	14m 52s
Scala CLI integration	17m 58s
ubuntu-latest jdk-8 unit tests 1 / 2	22m 17s
Mill integration	13m 24s
ubuntu-latest jdk-8 unit tests 2 / 2	16m 41s
LSP integration tests	32m 37s
Scala cross tests	58m 29s
Formatting	42s
Scalafix and docs	10m 6s
Sbt-metals/scripted jdk8	2m 8s
Scala javapc tests	3m 0s
Scala3 latest NIGHTLY cross test	4m 27s
MiMa	1m 20s
	6h 42m 37s

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