Update minecraft-server to the java17 line (2.0.0+up2026.8.2.java17)

Second of the three stage-3 publishes. Same chart content as
2.0.0+up2026.8.2.java8, only the published Java line changes: appVersion moves
to the dated tag 2026.8.2-java17 and the minecraft.version default moves to
1.20.1, which is the line's matching Minecraft version (Java 8 runs up to
1.16.5, 1.18-1.20.4 need Java 17, 1.20.5+ need Java 21).

minecraft-server/Chart.yaml

@@ -13,8 +13,8 @@ type: application
 # continuously, so a pod restart could pull a different image than the last one
 # without anything being recorded anywhere. The dated tags are immutable, so the
 # image is now pinned by the chart version like every other chart in this repo.
-version: 2.0.0+up2026.8.2.java8
-appVersion: "2026.8.2-java8"
+version: 2.0.0+up2026.8.2.java17
+appVersion: "2026.8.2-java17"
 
 maintainers:
   - name: jklein

minecraft-server/values.yaml

@@ -206,8 +206,8 @@ minecraft:
   # This value must match the Java line of the chart version: the image tag
   # comes from .Chart.AppVersion, so the JVM is fixed per published chart
   # version. Java 8 runs Minecraft up to 1.16.5, 1.18-1.20.4 need Java 17 and
-  # 1.20.5+ need Java 21. This chart publishes appVersion "2026.8.2-java8".
-  version: "1.12.2"
+  # 1.20.5+ need Java 21. This chart publishes appVersion "2026.8.2-java17".
+  version: "1.20.1"
 
 # curseforge, ftb and curseforgeServerpack are mutually exclusive - enabling
 # more than one is rejected by the chart (before 1.0.0 it silently rendered a