Update minecraft-server to the java17 line (1.0.0+upjava17)

PR B of three. Same chart as 1.0.0+upjava8, published for the second Java
line: appVersion selects the image tag, so the JVM is fixed per published
chart version.

minecraft.version moves with it (1.12.2 -> 1.20.1), because a Minecraft
version only runs on a matching JVM: Java 8 goes up to 1.16.5, 1.18-1.20.4
need Java 17. Since 1.0.0 this default is no longer overridden in the CI
values, so the install-test boots exactly this version and a mismatched
default would fail CI instead of passing on a CI-only override.

minecraft-server/Chart.yaml

@@ -8,8 +8,8 @@ type: application
 # The Java line of this chart version is chosen through appVersion, which is
 # the image tag: the chart is published once per line (java8 / java17 / java21)
 # and minecraft.version in values.yaml must match the line published here.
-version: 1.0.0+upjava8
-appVersion: "java8"
+version: 1.0.0+upjava17
+appVersion: "java17"
 
 maintainers:
   - name: jklein