Execute subcommand "positioned" now incorrectly conflicts with "at" and "as" subcommands

Steps to reproduce:

1. type the command /execute as @s positioned ^^^20 run summon pig
2. Run the command
3. Observe syntax error in chat
4. Observe that the predictive text does consider the syntax correct

Expected result: command should run as it did in 1.19.80 and earlier

Observed result: syntax error

This is annoying because you have to create a redundant execute to use the subcommand 

Work around: use the command:  /execute as @s run /execute positioned ^^^20 run summon pig