Rebalance Early magnetometer mass and power draw

[njits23]

I accidentally deleted the old PR for this change by updating my RP-1 fork's master branch. The original PR was here: #2449 and was apparently referencing the wrong branch.

[siimav]

Sounds like the tier 1 magnetometer experiment we have models something more advanced than what you sourced. The gigantic boom we have also doesn't quite fit the mass budget.

[njits23]

The first magnetometer experiment unlocks in the 1956-1960 science node. Additionally, don't forget this particular experiment is the only magnetometer that goes inside a probe core. It's more that the boom model is inappropriate for the year.

[njits23]

Additionally, the first video camera experiment is already modeled on Explorer VI, so it only makes sense to model other experiments from the same node on it as well

[njits23]

As far as I've been able to tell from looking at early probes, Mariner 2 (1962) and Mariner 4 (1964) weren't even really using boom-mounted magnetometers, but they were mounted away from the main bus.
Mariner 2, with the magnetometer below the omnidirectional antenna:

Mariner 3/4, with the Magnetometer on the omnidirectional antenna waveguide:

Considering how much earlier MG01 shows up in the tech tree, I do not consider it appropriate to model it as anything other than what spacecraft of that era like Sputnik 3 and Explorer VI were using: bus-mounted magnetometers.