t/op/infnan.t: Remove enclosing eval in "-Inf" to IV conversion test

As per review by @hvds in GH #19404, this test file doesn't have to worry
about whether `use integer` might fail.

t/op/infnan.t

@@ -578,9 +578,6 @@ cmp_ok('-1e-9999', '==', 0,     "underflow to 0 (runtime) from neg");
 
 # "-Inf" should be converted to IV consistently
 {
-    # Enclosed in a string eval so that majority of infnan.t are run
-    # before loading integer.pm, just in case.
-    eval <<'EOC';
     use integer;
     my $x = '-Inf';
     my $y = $NInf;      # $NInf and $y shall be NV -Inf
@@ -589,7 +586,6 @@ cmp_ok('-1e-9999', '==', 0,     "underflow to 0 (runtime) from neg");
     # $z shall be IV_MIN here, but as the actual value of IV_MIN is not
     # (easily) available in Perl so check its negative-ness as the next best.
     cmp_ok($z, '<', 0, "'-Inf' should be converted to a negative IV");
-EOC
 }
 
 done_testing();