align UUID reducer examples with allowed signatures (#3999)

# Description of Changes

- Corrected UUID v4/v7 reducer documentation examples to use valid
reducer signatures returning ()/Result<(), E>

# API and ABI breaking changes

- None

# Expected complexity level and risk

- 1 (doc example corrections only)

# Testing

- [ ] Not run (docs-only change)
- [ ] Please review documentation formatting and correctness

---------

Signed-off-by: miXin <52082254@qq.com>
Co-authored-by: Tyler Cloutier <cloutiertyler@users.noreply.github.com>
Co-authored-by: clockwork-labs-bot <clockwork-labs-bot@users.noreply.github.com>
Co-authored-by: Zeke Foppa <196249+bfops@users.noreply.github.com>

Author: 4 people

crates/bindings/src/lib.rs

@@ -1110,9 +1110,10 @@ impl ReducerContext {
     /// use spacetimedb::{reducer, ReducerContext, Uuid};
     ///
     /// #[reducer]
-    /// fn generate_uuid_v4(ctx: &ReducerContext) -> Uuid {
-    ///     let uuid = ctx.new_uuid_v4();
+    /// fn generate_uuid_v4(ctx: &ReducerContext) -> Result<(), Box<dyn std::error::Error>> {
+    ///     let uuid = ctx.new_uuid_v4()?;
     ///     log::info!(uuid);
+    ///     Ok(())
     /// }
     /// # }
     /// ```
@@ -1131,9 +1132,10 @@ impl ReducerContext {
     /// use spacetimedb::{reducer, ReducerContext, Uuid};
     ///
     /// #[reducer]
-    /// fn generate_uuid_v7(ctx: &ReducerContext) -> Result<Uuid, Box<dyn std::error::Error>> {
+    /// fn generate_uuid_v7(ctx: &ReducerContext) -> Result<(), Box<dyn std::error::Error>> {
     ///     let uuid = ctx.new_uuid_v7()?;
     ///     log::info!(uuid);
+    ///     Ok(())
     /// }
     /// # }
     /// ```