docs: Update description of iceberg.compression-codec (#26266)

## Description
Add a clarifying note to the description of
``iceberg.compression-codec`` in [Configuration
Properties](https://github.com/prestodb/presto/blob/master/presto-docs/src/main/sphinx/connector/iceberg.rst#configuration-properties)
in
[connector/iceberg.rst](https://github.com/prestodb/presto/blob/master/presto-docs/src/main/sphinx/connector/iceberg.rst)
about what compression codecs are available in a specific file format.

## Motivation and Context
Fixes #26261. 

## Impact
Documentation.

## Test Plan
Local doc build. See screenshot: 
<img width="624" height="139" alt="Screenshot 2025-10-09 at 2 42 06 PM"
src="https://github.com/user-attachments/assets/b93ca8d4-235b-4c8e-a13d-7afb2b00bbb6"
/>


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## Release Notes
```
== NO RELEASE NOTE ==
```

Author: steveburnett

presto-docs/src/main/sphinx/connector/iceberg.rst

@@ -347,7 +347,11 @@ Property Name                                           Description
 
 ``iceberg.compression-codec``                           The compression codec to use when writing files. The          ``GZIP``                           Yes                 No, write is not supported yet
                                                         available values are ``NONE``, ``SNAPPY``, ``GZIP``,
-                                                        ``LZ4``, and ``ZSTD``.
+                                                        and ``ZSTD``.
+                                                        
+                                                        Note: ``ZSTD`` is only available when 
+                                                        ``iceberg.file-format=ORC``.
+
 
 ``iceberg.max-partitions-per-writer``                   The maximum number of partitions handled per writer.          ``100``                            Yes                 No, write is not supported yet