toke.c: Remove dead code handling <FH> //

toke.c: Remove dead code handling <FH> //

A few lines of code added by this commit:

commit 6f33ba736d46c2f5bfdb2405fd09d82ec18a1d07
Author: Rafael Garcia-Suarez <rgarciasuarez@gmail.com>
Date:   Sun Aug 25 18:42:46 2002 +0000

    Fix parsing problems with the // operator.
    Make // able to follow various unary operators used without
    arguments or parens (shift, pop, getc, pos, readline,
    readlink, undef, umask, and the filetest operators), as
    well as the <FH> operator.

were already unreachable when they were added, specifically the code
for handling // after <FH> (which is fortunate, because XTERMORDORDOR
after <FH> would break <FH>+1).

S_scan_inputsymbol sets pl_yylval.ival to OP_NULL, since it has
already created the ops; it has done so since perl 5.000.  So this
branch is never reached when parsing <FH>.

The if-block containing these lines has had ‘|| op_type ==
OP_READLINE’ since perl 5.000, which has also always been redundant
for the same reason.