Build: Clarify generated code license entries

Describe the generated Thrift bindings using their actual sdist and wheel layouts, and align the Cython note with its licensing clarification.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: kevinjqliu

LICENSE

@@ -216,9 +216,10 @@ License: https://www.apache.org/licenses/LICENSE-2.0
 
 This product includes code from Apache Thrift.
 
-* Uses the fb303.thrift file that's part of Hive's thrift service, located in
-  vendor/fb303/ in the source distribution and shipped as the top-level fb303
-  package in binary distributions.
+* Includes Python bindings generated from the fb303.thrift file that's part of
+  Hive's thrift service. The bindings are located in vendor/fb303/ in source
+  distributions and shipped as the top-level fb303 package in binary
+  distributions.
 
 Copyright: 2006-2022 The Apache Software Foundation.
 Home page: https://thrift.apache.org/
@@ -228,26 +229,25 @@ License: https://www.apache.org/licenses/LICENSE-2.0
 
 This product includes code from Apache Hive.
 
-* Uses hive_metastore.thrift to generate the Hive Metastore client, located in
-  vendor/hive_metastore/ in the source distribution and shipped as the
-  top-level hive_metastore package in binary distributions.
+* Includes the Hive Metastore client generated from hive_metastore.thrift. The
+  generated code is located in vendor/hive_metastore/ in source distributions
+  and shipped as the top-level hive_metastore package in binary distributions.
 
 Copyright: 2008-2022 The Apache Software Foundation.
 Home page: https://hive.apache.org/
 License: https://www.apache.org/licenses/LICENSE-2.0
 
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-This product includes code from Cython in binary distributions.
+Official binary distributions contain the pyiceberg.avro.decoder_fast
+extension, built from C code generated by Cython.
 
-* The compiled extension module (pyiceberg.avro.decoder_fast) embeds the
-  Cython runtime code that Cython generates into every compiled module.
-  Cython's COPYING.txt states that this generated output is not a derivative
-  work of Cython and carries no additional license restrictions; Cython ships
-  no NOTICE file, so this entry is recorded for completeness only.
+* Cython generates this C code from pyiceberg/avro/decoder_fast.pyx. Cython
+  states that compilation may embed snippets in generated output, but that the
+  output is not a derivative work of Cython and those snippets impose no
+  license restrictions.
 
-Home page: https://cython.org/
-License: https://www.apache.org/licenses/LICENSE-2.0
-Notice: https://github.com/cython/cython/blob/master/COPYING.txt
+Cython licensing clarification:
+https://github.com/cython/cython/blob/2f3a781dcca092ce95fbfef2736b12b0d1ab50dd/COPYING.txt
 
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