ffi: move the dependency override from ffi/Cargo.toml to the root one

[jmartinesp]

This seems to be the only way to make the log rotation fix work and avoid build warnings like:

warning: patch for the non root package will be ignored, specify patch at the workspace root:
package:   matrix-rust-sdk/bindings/matrix-sdk-ffi/Cargo.toml
workspace: = matrix-rust-sdk/Cargo.toml
    Finished `dev` profile [unoptimized] target(s) in 0.30s

I can confirm log rotation was working fine on an Android client after these changes, while it's not working with the current code on main.

Fixes the implementation in #4038.

• Public API changes documented in changelogs (optional)

Signed-off-by:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.51%. Comparing base (ac61fc8) to head (58b8695).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4044      +/-   ##
==========================================
+ Coverage   84.50%   84.51%   +0.01%     
==========================================
  Files         266      266              
  Lines       28512    28512              
==========================================
+ Hits        24093    24098       +5     
+ Misses       4419     4414       -5     

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