Update CHANGELOG.md

CHANGELOG.md

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 ### ClickHouse release v20.3.2.1, 2020-03-12
 
-### Backward Incompatible Changes
+### Backward Incompatible Change
 
 * Fixed the issue `file name too long` when sending data for `Distributed` tables for a large number of replicas. Fixed the issue that replica credentials were exposed in the server log. The format of directory name on disk was changed to `[shard{shard_index}[_replica{replica_index}]]`. [#8911](https://github.com/ClickHouse/ClickHouse/pull/8911) ([Mikhail Korotov](https://github.com/millb)) After you upgrade to the new version, you will not be able to downgrade without manual intervention, because old server version does not recognize the new directory format. If you want to downgrade, you have to manually rename the corresponding directories to the old format. This change is relevant only if you have used asynchronous `INSERT`s to `Distributed` tables. In the version 20.3.3 we will introduce a setting that will allow you to enable the new format gradually.
 * Changed the format of replication log entries for mutation commands. You have to wait for old mutations to process before installing the new version.
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 * Add function `moduloOrZero` [#9358](https://github.com/ClickHouse/ClickHouse/pull/9358) ([hcz](https://github.com/hczhcz))
 * Added system tables `system.zeros` and `system.zeros_mt` as well as tale functions `zeros()` and `zeros_mt()`. Tables (and table functions) contain single column with name `zero` and type `UInt8`. This column contains zeros. It is needed for test purposes as the fastest method to generate many rows. This fixes [#6604](https://github.com/ClickHouse/ClickHouse/issues/6604) [#9593](https://github.com/ClickHouse/ClickHouse/pull/9593) ([Nikolai Kochetov](https://github.com/KochetovNicolai))
 
-### Experimental Features
+### Experimental Feature
 * Add new compact format of parts in `MergeTree`-family tables in which all columns are stored in one file. It helps to increase performance of small and frequent inserts. The old format (one file per column) is now called wide. Data storing format is controlled by settings `min_bytes_for_wide_part` and `min_rows_for_wide_part`. [#8290](https://github.com/ClickHouse/ClickHouse/pull/8290) ([Anton Popov](https://github.com/CurtizJ))
 * Support for S3 storage for `Log`, `TinyLog` and `StripeLog` tables. [#8862](https://github.com/ClickHouse/ClickHouse/pull/8862) ([Pavel Kovalenko](https://github.com/Jokser))