IMPALA-12692 : [DOCS] Typo in docs about random() function

Changed name of random fucntion in impala_math_functions.xml
from "RANDOME(), RANDOME(BIGINT seed)" to "RANDOM(), RANDOM(BIGINT seed)"

Change-Id: I4844eb8d155326081c385d88b98a591dbbde7369
Reviewed-on: http://gerrit.cloudera.org:8080/21126
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
Reviewed-by: Michael Smith <michael.smith@cloudera.com>

docs/topics/impala_math_functions.xml

@@ -1463,7 +1463,7 @@ select pmod(5,-2);
       <dlentry id="rand">
 
         <dt>
-          RAND(), RAND(BIGINT seed), RANDOME(), RANDOME(BIGINT seed)
+          RAND(), RAND(BIGINT seed), RANDOM(), RANDOM(BIGINT seed)
         </dt>
 
         <dd>