[Rust Server] Fix homepage URL in Cargo.toml (#19365)

This fixes a missing quote in Cargo.toml, which causes validation errors

Author: richardwhiuk

modules/openapi-generator/src/main/resources/rust-server/Cargo.mustache

@@ -28,7 +28,7 @@ repository = "{{.}}"
 documentation = "{{.}}"
 {{/documentationUrl}}
 {{#homePageUrl}}
-homepage = "{{.}}
+homepage = "{{.}}"
 {{/homePageUrl}}
 
 [features]