Update GA4Client version to 1.2.0

Bug Fixes

• Flatten product.Attributes to be on the product level (#41) (ee03770)
• Map CouponCode to reserved attributes coupon (#50) (f7380d4)
• Prevent attribute cleansing when data cleansing is disabled (#52) (9847bf8)
• Re-map affiliation from event level to item level (#51) (b7dfef8)
• Update package.json (#39) (d4ea321)

Features

• Limit commerce event attributes to 100 keys (#47) (1813a98)
• Limit event attributes to 100 keys (#40) (057543b)
• Limit item params to 10 non-reserved keys (#49) (7670d99)
• Standardize Names Keys and Values (#36) (f3e5aa1)