I could see arguments for either 6th caster level or 7th caster level, but either way, your Shocking Grasp would only do 5d6 damage.
Caster Level 6th
You have two traits that add to caster level. Thus, you have two trait bonuses to caster level. However, trait bonuses do not stack:
A trait bonus is a bonus granted via a character trait. Character traits are an optional additional character defining feature like feats but less powerful (typically about half as strong as a feat.) As with other named bonuses, trait bonuses do not "stack" with other trait bonuses.
Therefore, your caster level takes the higher of the two bonuses (which is from Magical Knack) and is 6th. (4 Magus + 2 Magical Knack)
Caster Level 7th
If you can convince your DM that Lore Seeker's effect is not a trait bonus - after all, the word "bonus" is never used to describe the caster level modifier. Then you could further argue that Magical Knack applies first and Lore seeker second, and if your DM buys all of that, you can get an extra caster level.
If I were your DM, I would not allow that logic. Your mileage may vary.
...And none of that matters for Shocking Grasp anyway
Shocking Grasp is capped at 5d6, regardless of what your caster level is.
Your successful melee touch attack deals 1d6 points of electricity damage per caster level (maximum 5d6). When delivering the jolt, you gain a +3 bonus on attack rolls if the opponent is wearing metal armor (or is carrying a metal weapon or is made of metal).
Might be useful for other spells, though.