fix: Remote signing with table specific s3.signer.endpoint (#2005)

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# Rationale for this change
Currently pyiceberg remote singing only works if the sign endpoint is
shared by all tables in a REST Catalog.
However, some Catalogs use table specific endpoints.

If table specific endpoints are used, Pyiceberg sends the sign request
for the second table that is queried to the sign endpoint of the first
table.
The reason for this is, that although we [re-register() a new signer
with different
properties](https://github.com/apache/iceberg-python/blob/996a7ba4dbf4afdb3d46689f1715206b1c355f2a/pyiceberg/io/fsspec.py#L166),
this statement has no effect the second time it runs because of the
unique_id, even if the properties are different.

https://github.com/boto/botocore/blob/8c517320c6a40cd91e8e7fbb05e27183ba2f6dce/botocore/hooks.py#L310-L312

This PR first unregisters the old handler, before adding the new one.

# Are these changes tested?
No. Any idea how we could test them?
Just tested against LAKEKEEPER in a notebook while implementing table
specific endpoints.

# Are there any user-facing changes?
It works now!
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Author: c-thiel

pyiceberg/io/fsspec.py

@@ -163,6 +163,7 @@ def _s3(properties: Properties) -> AbstractFileSystem:
     fs = S3FileSystem(client_kwargs=client_kwargs, config_kwargs=config_kwargs)
 
     for event_name, event_function in register_events.items():
+        fs.s3.meta.events.unregister(event_name, unique_id=1925)
         fs.s3.meta.events.register_last(event_name, event_function, unique_id=1925)
 
     return fs