Remove old guards for before 3.0

- logger 1.4.2 since ruby 2.7.0
- matrix 0.3.1 since ruby 3.0.0
- stringio 3.0.0 since ruby 3.0.0

library/logger/device/close_spec.rb

@@ -15,17 +15,8 @@
     rm_r @file_path
   end
 
-  version_is Logger::VERSION, ""..."1.4.0" do
-    it "closes the LogDevice's stream" do
-      @device.close
-      -> { @device.write("Test") }.should complain(/\Alog writing failed\./)
-    end
-  end
-
-  version_is Logger::VERSION, "1.4.0" do
-    it "closes the LogDevice's stream" do
-      @device.close
-      -> { @device.write("Test") }.should complain(/\Alog shifting failed\./)
-    end
+  it "closes the LogDevice's stream" do
+    @device.close
+    -> { @device.write("Test") }.should complain(/\Alog shifting failed\./)
   end
 end

library/logger/device/write_spec.rb

@@ -35,17 +35,8 @@
     rm_r path
   end
 
-  version_is Logger::VERSION, ""..."1.4.0" do
-    it "fails if the device is already closed" do
-      @device.close
-      -> { @device.write "foo" }.should complain(/\Alog writing failed\./)
-    end
-  end
-
-  version_is Logger::VERSION, "1.4.0" do
-    it "fails if the device is already closed" do
-      @device.close
-      -> { @device.write "foo" }.should complain(/\Alog shifting failed\./)
-    end
+  it "fails if the device is already closed" do
+    @device.close
+    -> { @device.write "foo" }.should complain(/\Alog shifting failed\./)
   end
 end

library/matrix/unitary_spec.rb

@@ -14,10 +14,8 @@
       Matrix[[0, Complex(0, 1)], [Complex(0, 1), 0]].should.unitary?
     end
 
-    version_is((Matrix::const_defined?(:VERSION) ? Matrix::VERSION : "0.1.0"), "0.3.0") do
-      it "returns true for unitary matrices with a Complex and a negative #imag" do
-        Matrix[[0, Complex(0, 1)], [Complex(0, -1), 0]].should.unitary?
-      end
+    it "returns true for unitary matrices with a Complex and a negative #imag" do
+      Matrix[[0, Complex(0, 1)], [Complex(0, -1), 0]].should.unitary?
     end
 
     it "raises an error for rectangular matrices" do

library/stringio/initialize_spec.rb

@@ -294,14 +294,9 @@
     io.string.encoding.should == Encoding::EUC_JP
   end
 
-  guard_not -> { # [Bug #16497]
-    stringio_version = StringIO.const_defined?(:VERSION) ? StringIO::VERSION : "0.0.2"
-    version_is(stringio_version, "0.0.3"..."0.1.1")
-  } do
-    it "the #external_encoding to the encoding of the String when passed a String" do
-      s = ''.force_encoding(Encoding::EUC_JP)
-      io = StringIO.new(s)
-      io.external_encoding.should == Encoding::EUC_JP
-    end
+  it "the #external_encoding to the encoding of the String when passed a String" do
+    s = ''.force_encoding(Encoding::EUC_JP)
+    io = StringIO.new(s)
+    io.external_encoding.should == Encoding::EUC_JP
   end
 end