Suppress warnings in these tests

[chainsawriot]

In light of #409 and #411

 ══ Warnings ════════════════════════════════════════════════════════════════════
1. Export / Import to .R dump file ('test_format_R.R:7:9') - The `trust` argument of `import()` should be explicit for serialization formats
as of rio 1.0.3.
ℹ Missing `trust` will be set to FALSE by default for .R in 2.0.0.

2. Export / Import to .R dump file ('test_format_R.R:13:9') - The `trust` argument of `import()` should be explicit for serialization formats
as of rio 1.0.3.
ℹ Missing `trust` will be set to FALSE by default for dump in 2.0.0.

3. Export to and import from Rdata ('test_format_rdata.R:6:9') - The `trust` argument of `import()` should be explicit for serialization formats
as of rio 1.0.3.
ℹ Missing `trust` will be set to FALSE by default for RData in 2.0.0.

4. Export to and import from rds ('test_format_rds.R:5:9') - The `trust` argument of `import()` should be explicit for serialization formats
as of rio 1.0.3.
ℹ Missing `trust` will be set to FALSE by default for RDS in 2.0.0.

[chainsawriot]

Or simply trust them.