gst1-python3: make sure python3 is used
gst1-python3: make sure python3 is used

According to @jnbr this change should fix the package which
erroneously seems to detect python2 when being configured.

Closes: #10432

coredumb/void-packages,NeoChontrix/void-packages,necrophcodr/void-packages,floGik/void-packages,coredumb/void-packages,floGik/void-packages,NeoChontrix/void-packages,floGik/void-packages,coredumb/void-packages,coredumb/void-packages,necrophcodr/void-packages,NeoChontrix/void-packages,NeoChontrix/void-packages,coredumb/void-packages,necrophcodr/void-packages,necrophcodr/void-packages,necrophcodr/void-packages,NeoChontrix/void-packages,NeoChontrix/void-packages,floGik/void-packages,floGik/void-packages,floGik/void-packages,coredumb/void-packages