Use correct case

The IP Risk model has not been released yet so this won't impact
anyone.

Author: oschwald

src/main/java/com/maxmind/geoip2/model/IpRiskResponse.java

@@ -81,7 +81,7 @@ public IpRiskResponse(
      * @return The IP risk of a model.
      */
     @JsonProperty("ip_risk")
-    public double getIPRisk() {
+    public double getIpRisk() {
         return this.ipRisk;
     }
 }

src/test/java/com/maxmind/geoip2/DatabaseReaderTest.java

@@ -243,7 +243,7 @@ public void testIPRisk() throws Exception {
             assertFalse(response.isResidentialProxy());
             assertFalse(response.isTorExitNode());
             assertEquals(ipAddress.getHostAddress(), response.getIpAddress());
-            assertEquals(0.1, response.getIPRisk(), 0.0001);
+            assertEquals(0.1, response.getIpRisk(), 0.0001);
             assertEquals("0:0:0:0:0:0:d602:300/126", response.getNetwork().toString());
             IpRiskResponse tryResponse = reader.tryIpRisk(ipAddress).get();
             assertEquals(response.toJson(), tryResponse.toJson());