test(lib): use registry-mock

[KSXGitHub]

I forgot that the workspace member package-manager also has a test that relies on the registry.

[github-actions[bot]]

Micro-Benchmark Results

Linux

group                          main                                   pr
-----                          ----                                   --
tarball/download_dependency    1.00      6.7±0.36ms   649.7 KB/sec    1.00      6.7±0.22ms   648.8 KB/sec

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (bd7002a) 87.01% compared to head (e7d5f79) 87.05%. Report is 4 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #205 +/- ## ========================================== + Coverage 87.01% 87.05% +0.03% ========================================== Files 56 56 Lines 2827 2828 +1 ========================================== + Hits 2460 2462 +2 + Misses 367 366 -1 ```

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Integrated-Benchmark Report (Linux)

Scenario: Frozen Lockfile

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
pacquet@HEAD	144.2 ± 11.2	128.2	163.4	1.05 ± 0.11
pacquet@main	137.6 ± 10.1	125.5	155.6	1.00

BENCHMARK_REPORT.json

```json { "results": [ { "command": "pacquet@HEAD", "mean": 0.1442323217215385, "stddev": 0.011218107725278842, "median": 0.14426684926000002, "user": 0.06799588153846153, "system": 0.19912513230769233, "min": 0.12819780126000002, "max": 0.16337741526000002, "times": [ 0.15971287326000003, 0.14539305226000002, 0.15101664526000003, 0.13817071326000002, 0.13103303526, 0.13695294726, 0.16337741526000002, 0.14426684926000002, 0.14000733426, 0.15595238326000002, 0.12819780126000002, 0.13175156026, 0.14918757226 ], "exit_codes": [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ] }, { "command": "pacquet@main", "mean": 0.13757958766, "stddev": 0.010082026144680185, "median": 0.13423094826, "user": 0.06276402, "system": 0.2071453066666666, "min": 0.12548955426000002, "max": 0.15556016326000002, "times": [ 0.13420533826000003, 0.15270394426000003, 0.15556016326000002, 0.12602332726, 0.14865475226000002, 0.12740181026000003, 0.13423094826, 0.14910927126, 0.12683968826000003, 0.13178286326000002, 0.14254325626000003, 0.13477913526000002, 0.12548955426000002, 0.14091178626, 0.13345797626000003 ], "exit_codes": [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ] } ] } ```