Remove rules_jvm_external dependency once stardoc has upgraded to 6.2

There's a FIXME in the MODULE.bazel:

# FIXME: Remove this once stardoc has updated its `rules_jvm_external` dependency to at least 6.2. See: https://github.com/bazel-contrib/rules_jvm_external/issues/1177
bazel_dep(name = "rules_jvm_external", version = "6.2", dev_dependency = True)