fix upgrade notes

Author: haileyajohnson

docs/src/site/pages/netcdfJava/Upgrade.md

@@ -31,8 +31,10 @@ As such, we no longer utilize WebStart.
 ## netCDF-Java API Changes (5.5.x)
 
 Point release notes:
-* [5.5.0](https://github.com/Unidata/netcdf-java/releases/tag/v5.5.0){:target="_blank"} (_2021-12-20_)
-
+* [5.5.1](https://github.com/Unidata/netcdf-java/releases/tag/v5.5.1){:target="_blank"} (_2021-12-20_)
+* `5.5.0` was released but not announced.
+  It should not be used.
+  
 5.5.x is the first release that includes read support for [Zarr](https://zarr.readthedocs.io/en/stable/index.html){:target="_blank"}. 
 There is also a new package for filters, `ucar.ma2.filters`, which allows user-provided compressors and filters to be supplied through a [Service Provider Interface](https://www.baeldung.com/java-spi){:target="_blank"}.