HFM typo fixed and test fixed (#108804)

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Fix typo in HistogramFieldMapper  and fixed related test code

closes https://github.com/elastic/elasticsearch/issues/108050

x-pack/plugin/analytics/src/main/java/org/elasticsearch/xpack/analytics/mapper/HistogramFieldMapper.java

@@ -410,7 +410,7 @@ public class HistogramFieldMapper extends FieldMapper {
                         + name()
                         + "] of type ["
                         + typeName()
-                        + "] doesn't not support indexing multiple values for the same field in the same document"
+                        + "] doesn't support indexing multiple values for the same field in the same document"
                 );
             }
             context.doc().addWithKey(fieldType().name(), field);

x-pack/plugin/analytics/src/test/java/org/elasticsearch/xpack/analytics/mapper/HistogramFieldMapperTests.java

@@ -87,7 +87,7 @@ public class HistogramFieldMapperTests extends MapperTestCase {
         })));
         assertThat(
             e.getCause().getMessage(),
-            containsString("doesn't not support indexing multiple values for the same field in the same document")
+            containsString("doesn't support indexing multiple values for the same field in the same document")
         );
     }