Fix snapshot doc publishing after f1308a0

```
rsync: [sender] change_dir "/home/runner/work/error-prone/error-prone/target/site/apidocs" failed: No such file or directory (2)
rsync error: some files/attrs were not transferred (see previous errors) (code 23) at main.c(1338) [sender=3.2.7]
```

https://github.com/google/error-prone/actions/runs/11855327714/job/33039721727

PiperOrigin-RevId: 696903927

util/generate-latest-docs.sh

@@ -28,7 +28,7 @@ git clone --quiet --branch=gh-pages https://x-access-token:${GITHUB_TOKEN}@githu
 )
 
 mvn -P '!examples' javadoc:aggregate
-rsync -a target/site/apidocs/ ${GH_PAGES_DIR}/api/latest
+rsync -a target/reports/apidocs/ ${GH_PAGES_DIR}/api/latest
 
 # The "mvn clean" is necessary since the wiki docs are generated by an
 # annotation processor that also compiles the code.  If Maven thinks the code