fix: remove unintentional default-features=false for azure_data_cosmos workspace dep (#4219)

## Problem

The merge commit e753b8e ("Merge branch 'main' into
release/azure_data_cosmos-previews") introduced a new
`[workspace.dependencies.azure_data_cosmos]` block with
`default-features = false`. This block did not exist in either merge
parent — it was created during conflict resolution, modeled after the
`azure_data_cosmos_driver` block which legitimately disables defaults.

With default features disabled, the `reqwest` feature is no longer
enabled for downstream workspace crates like `azure_data_cosmos_perf`.
This causes a compilation failure because `cosmos_client_builder.rs`
uses `COSMOS_ALLOWED_HEADERS` and
`AZURE_COSMOS_PER_PARTITION_CIRCUIT_BREAKER_ENABLED` unconditionally,
but their imports are gated behind `#[cfg(feature = "reqwest")]`:

```
error[E0425]: cannot find value `COSMOS_ALLOWED_HEADERS` in this scope
  --> sdk/cosmos/azure_data_cosmos/src/clients/cosmos_client_builder.rs:312:27

error[E0425]: cannot find value `AZURE_COSMOS_PER_PARTITION_CIRCUIT_BREAKER_ENABLED` in this scope
  --> sdk/cosmos/azure_data_cosmos/src/clients/cosmos_client_builder.rs:371:27
```

## Impact

This broke the AKS perf CronJob (`cosmos-perf-updater`) in
`rg-cosmos-perf-pr4159`. The updater correctly detected the new commit
and attempted to rebuild, but the Docker image build fails due to the
compilation error above. The perf workload is stuck on commit
`0b99c1158` and cannot auto-update.

## Fix

Remove `default-features = false` from the
`[workspace.dependencies.azure_data_cosmos]` block. This restores the
default feature set (which includes `reqwest`) and allows the perf crate
to compile.

## Verification

- Neither merge parent had this workspace dependency block, confirming
it was introduced during conflict resolution
- `main` branch does not have a
`[workspace.dependencies.azure_data_cosmos]` block at all
- The `azure_data_cosmos` crate's default features include `reqwest`,
which is required for the unconditional use of `COSMOS_ALLOWED_HEADERS`
and `AZURE_COSMOS_PER_PARTITION_CIRCUIT_BREAKER_ENABLED`

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

Author: tvaron3

Cargo.toml

@@ -94,7 +94,6 @@ path = "sdk/storage/azure_storage_blob"
 version = "0.12.0"
 
 [workspace.dependencies.azure_data_cosmos]
-default-features = false
 version = "0.33.0"
 path = "sdk/cosmos/azure_data_cosmos"