update iris to use stdpp

1 job for ci in 14 minutes and 13 seconds (queued for 12 minutes and 13 seconds)
Status Job ID Name Coverage
  Test
failed #2543
lrust-coq8.6

00:14:13

 
Name Stage Failure
failed
lrust-coq8.6 Test There is an unknown failure, please try again
make[1]: *** [theories/typing/unsafe/refcell/refmut_code.vo] Error 1
make[1]: Leaving directory '/builds/FP/LambdaRust-coq'
Makefile:11: recipe for target 'all' failed
make: *** [all] Error 2

real 9m55.552s
user 18m46.067s
sys 0m8.137s
ERROR: Build failed: exit code 1