Remove `extern crate prusti_contracts` from Prusti

[JonasAlaif]

[Aurel300]

Thanks, this was also bugging me.

[JonasAlaif]

bors r+

[bors[bot]]

Build succeeded:

• all-tests (macos-latest)
• all-tests (ubuntu-latest)
• all-tests (windows-latest)
• clippy-check
• fmt-check
• purification-tests
• smir-check
• test-crates

[zgrannan]

Finished benchmarking commit (c449775827cf7227253197dd9c2563e04953a62e): comparison url.

Benchmark returns the average of 3 consecutive runs of the benchmark suite, performed after an initial 'warm-up' run. An external Prusti server is maintained over the 4 runs.

Wall time

This benchmark run did not return any relevant results for this metric.

Instruction count (excludes Viper)

This benchmark run did not return any relevant results for this metric.

Cycles (excludes Viper)

Results

• Primary benchmarks: 🎉 relevant improvement found
• Secondary benchmarks: no relevant changes found

	mean[^1]	max	count[^2]
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	N/A	N/A	0
Improvements 🎉 (primary)	-2.0%	-2.0%	1
Improvements 🎉 (secondary)	N/A	N/A	0
All 😿🎉 (primary)	-2.0%	-2.0%	1

[^1]: the arithmetic mean of the percent change [^2]: number of relevant changes

If you disagree with this performance assessment, please file an issue in prusti-dev/prusti-perf.

@rustbot label: -perf-regression