fix(API): Remove irrelevant resamp_rate property

[epage]

This is only relevant to SignalsWaveform and will be re-added by #161.

Fixes #121.

BREAKING CHANGE: session.signals no longer has a resamp_rate property.
This never worked anyways so it shouldn't impact anyone.

• This contribution adheres to CONTRIBUTING.md.
• New tests have been created for any new features or regression tests for bugfixes.
• tox successfully runs, including unit tests and style checks (see CONTRIBUTING.md).

[coveralls]

Coverage increased (+0.009%) to 64.185% when pulling a7b8f65 on epage:resamp into 5590c92 on ni:master.

[coveralls]

Coverage increased (+0.009%) to 64.185% when pulling a7b8f65 on epage:resamp into 5590c92 on ni:master.

[coveralls]

Coverage increased (+0.009%) to 64.185% when pulling a7b8f65 on epage:resamp into 5590c92 on ni:master.

[coveralls]

Coverage increased (+0.009%) to 64.185% when pulling a7b8f65 on epage:resamp into 5590c92 on ni:master.

[coveralls]

Coverage increased (+0.003%) to 64.179% when pulling b5b0197 on epage:resamp into 5590c92 on ni:master.