Test gauge type weight

[jubeira]

Test zeroing out gauge type weight:

• earned BAL can be claimed after setting weight to 0
• no more emissions afterwards

To double check,

• comment it block setting weight to 0
• comment extra weight check:

    const gaugeWeightAfter = await gauge.getCappedRelativeWeight(await currentTimestamp());
    expect(gaugeWeightAfter).to.be.eq(0);

• last test mint tokens (3 - no emissions) should fail (tokens would have been minted if weight was not 0)