docs: Update readme to reflect tracing feature is needed for read-table

[OussamaSaoudi-db]

What changes are proposed in this pull request?

Updates the docs to reflect that tracing is required to be enabled in the read_table.c example code.

How was this change tested?

Compiling without the tracing feature yields the following error:

Undefined symbols for architecture arm64:
  "_enable_event_tracing", referenced from:
      _main in read_table.c.o

And compiling with it works.

[OussamaSaoudi-db]

The error comes from this line in read_table.c.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.45%. Comparing base (ba37b62) to head (4ca2f36).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #619      +/-   ##
==========================================
+ Coverage   83.43%   83.45%   +0.01%     
==========================================
  Files          75       75              
  Lines       16922    16922              
  Branches    16922    16922              
==========================================
+ Hits        14119    14122       +3     
  Misses       2146     2146              
+ Partials      657      654       -3     

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[nicklan]

ugg this is a bit of a mess. thanks for noticing this. So, default-engine is a "default" feature in the ffi crate. So you'd have to do --no-default-features to not get it, and then read-table would break.

So probably just update the docs to specify that you should enable the tracing feature and remove any mention of the default-engine one for now.

@zachschuermann, let's add this to the list of things we need to fix when we look at feature flags again.