Fix name of G2 GLONASS frequency

Thanks Bryan!

src/changes/changes.xml

@@ -33,6 +33,9 @@
              as updates to AbstractDetector, AbstractGNSSAttitudeProvider, DragSensitive,
              RadiationSensitive, and ZipJarCrawler. See the list below for a full
              description of the changes.">
+      <action dev="evan" type="fix">
+        Fix  name of GLONASS G2 frequency.
+      </action>
       <action dev="luc" type="fix" >
         Fixed accuracy of dates conversions from java dates.
       </action>

src/main/java/org/orekit/gnss/Frequency.java

@@ -41,7 +41,7 @@ public enum Frequency {
     R02(SatelliteSystem.GLONASS, "G2", 1246.0 / 10.23),
 
     /** GLONASS, "G3" (1202.025 MHz). */
-    R03(SatelliteSystem.GLONASS, "G2", 117.5),
+    R03(SatelliteSystem.GLONASS, "G3", 117.5),
 
     /** Galileo, "E1" (1575.42 MHz). */
     E01(SatelliteSystem.GALILEO, "E1", 154),