Revert "Cr2Decoder: read black/white levels from ColorData4 ver.3"

After further analysis, it does not look like either one of these
is `SpecularWhiteLevel` for that camera. Probably it simply isn't there.

https://discuss.pixls.us/t/any-canon-eos-40d-users-around-a-bit-of-testing-wanted/40843
exiftool/exiftool#233

This reverts commit bd9074a.
This reverts commit ccb06f6.

data/cameras.xml

@@ -318,6 +318,7 @@
 			<Color x="1" y="1">BLUE</Color>
 		</CFA>
 		<Crop x="30" y="18" width="3908" height="2602"/>
+		<Sensor black="1021" white="13600"/>
 		<BlackAreas>
 			<Vertical x="0" width="28"/>
 			<Horizontal y="4" height="12"/>
@@ -333,6 +334,7 @@
 	<Camera make="Canon" model="Canon EOS 40D" mode="sRaw1">
 		<ID make="Canon" model="EOS 40D">Canon EOS 40D</ID>
 		<Crop x="0" y="0" width="0" height="0"/>
+		<Sensor black="0" white="16383"/>
 		<Hints>
 			<Hint name="sraw_40d" value=""/>
 		</Hints>
@@ -347,6 +349,7 @@
 	<Camera make="Canon" model="Canon EOS 40D" mode="sRaw2">
 		<ID make="Canon" model="EOS 40D">Canon EOS 40D</ID>
 		<Crop x="0" y="0" width="1944" height="1296"/>
+		<Sensor black="0" white="16383"/>
 		<Hints>
 			<Hint name="sraw_40d" value=""/>
 		</Hints>

src/librawspeed/decoders/Cr2Decoder.cpp

@@ -318,9 +318,8 @@ getBlackAndWhiteLevelOffsetsInColorData(ColorDataFormat f,
   case ColorData4:
     switch (colorDataVersion) {
     case 2:
-      return std::nullopt; // Still no `SpecularWhiteLevel`.
     case 3:
-      return {{231, 629}};
+      return std::nullopt; // Still no `SpecularWhiteLevel`.
     case 4:
     case 5:
       return {{692, 697}};