README: fix the base name for polarssl

1 job for bugfix/julien/update-readme in 59 minutes and 26 seconds
Status Name Job ID Coverage
  Test
failed build #403267
docker

00:59:26

 
Name Stage Failure
failed
build Test
Removing ioccc/.frama-c/2020_otterness_prog.parse/parse.log
Removing ioccc/.frama-c/2020_otterness_prog.parse/stats.txt

Skipping Git submodules setup
Executing "step_script" stage of the job script
$ make -B all >/dev/null
make[1]: *** [/usr/local/share/frama-c/analysis-scripts//analysis.mk:190: 2019_adamovsky_prog.eva] Error 1
make: *** [Makefile:99: ioccc] Error 2
ERROR: Job failed: exit code 1