biology/psi88: Unbreak build with GCC 10

ctplot.f:69:29:

69 |       CALL SYMBOL (XA,YA,.15,STRING,ANGLE,K)
   |                             1

Error: Rank mismatch in argument 'string' at (1) (scalar and rank-1)

http://package18.nyi.freebsd.org/data/121amd64-default-PR244494/2020-06-10_18h04m44s/logs/errors/psi88-1.0_16.log

PR: 246700