updated release notes more

Author: edwardhartnett

RELEASE_NOTES.md

@@ -7,6 +7,7 @@ This file contains a high-level description of this package's evolution. Release
 
 ## 4.7.3 - TBD
 
+* [Bug Fix] Library was modified so that rewriting the same attribute happens without deleting the attribute, to avoid a limit on how many times this may be done in HDF5. This fix was thought to be in 3.6.2 but was not. See [https://github.com/Unidata/netcdf-c/issues/350].
 * [Enhancement] Add a dispatch version number to netcdf_meta.h and libnetcdf.settings, in case we decide to change dispatch table in future. See [https://github.com/Unidata/netcdf-c/issues/1469].
 * [Bug Fix] Now testing that endianness can only be set on atomic ints and floats. See [https://github.com/Unidata/netcdf-c/issues/1479].
 * [Bug Fix] Fix for subtle error involving var and unlimited dim of the same name, but unrelated, in netCDF-4. See [https://github.com/Unidata/netcdf-c/issues/1496].