[stardoc] Update stardoc to 7.0.0

Of special note:
> The Markdown renderer now uses Google EscapeVelocity instead of Apache Velocity for templating. The templating engines are almost compatible, with the exception of escapes in string literals: if in your template you had a string literal with a character escape, you would need to expand it.

[Release Notes for 0.6.0](https://github.com/bazelbuild/stardoc/releases/tag/0.6.0)

"almost", indeed. :/

fixes #1203

MODULE.bazel

@@ -89,7 +89,7 @@ maven.install(
 use_repo(maven, "kotlin_rules_maven", "unpinned_kotlin_rules_maven")
 
 bazel_dep(name = "rules_pkg", version = "0.7.0")
-bazel_dep(name = "stardoc", version = "0.5.6", repo_name = "io_bazel_stardoc")
+bazel_dep(name = "stardoc", version = "0.7.0", repo_name = "io_bazel_stardoc")
 bazel_dep(name = "rules_proto", version = "5.3.0-21.7")
 
 bazel_dep(name = "rules_testing", version = "0.5.0", dev_dependency = True)