arm64: dts: ti: k3-j721e-common-proc-board: Remove duplicated main_i2c1_exp4_pins_default

Two pimux entry is present with the same name, remove one of them.

Fixes: cb27354b ("arm64: dts: ti: k3-j721e: Add DT nodes for few peripherials")
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>