Move non-linux specs for Rational exponents with ArgumentErrors

The check for ArgumentError is performed within Ruby itself, and
unrelated to bugs in pow() in glibc. These specs should run on Linux
too.

shared/rational/exponent.rb

@@ -122,6 +122,24 @@
           (Rational(fixnum_max) ** -bignum_value)
         }.should raise_error(ArgumentError)
       end
+
+      it "raises an ArgumentError when self is < -1" do
+        -> {
+          (Rational(-2) ** bignum_value)
+        }.should raise_error(ArgumentError)
+        -> {
+          (Rational(fixnum_min) ** bignum_value)
+        }.should raise_error(ArgumentError)
+      end
+
+      it "raises an ArgumentError when self is < -1 and the exponent is negative" do
+        -> {
+          (Rational(-2) ** -bignum_value)
+        }.should raise_error(ArgumentError)
+        -> {
+          (Rational(fixnum_min) ** -bignum_value)
+        }.should raise_error(ArgumentError)
+      end
     end
 
     # Fails on linux due to pow() bugs in glibc: http://sources.redhat.com/bugzilla/show_bug.cgi?id=3866
@@ -148,26 +166,6 @@
           }.should complain(/warning: in a\*\*b, b may be too big/)
         end
       end
-
-      ruby_version_is "3.4" do
-        it "raises an ArgumentError when self < -1" do
-          -> {
-            (Rational(-2) ** bignum_value)
-          }.should raise_error(ArgumentError)
-          -> {
-            (Rational(fixnum_min) ** bignum_value)
-          }.should raise_error(ArgumentError)
-        end
-
-        it "raises an ArgumentError when self is < -1 and the exponent is negative" do
-          -> {
-            (Rational(-2) ** -bignum_value)
-          }.should raise_error(ArgumentError)
-          -> {
-            (Rational(fixnum_min) ** -bignum_value)
-          }.should raise_error(ArgumentError)
-        end
-      end
     end
   end