Change Kanuri autonym to lowercase

In Kanuri, the name of the language is specifically
written in lowercase, according to
"Dictionary of the Kanuri Language"
Edited by: Norbert Cyffer and John Hutchinson
De Gruyter 1990.

data/langdb.yaml

@@ -333,7 +333,7 @@ languages:
   ko: [Kore, [AS], 한국어]
   koi: [Cyrl, [EU], перем коми]
   koy: [Latn, [AM], "Denaakkenaageʼ"]
-  kr: [Latn, [AF], Kanuri]
+  kr: [Latn, [AF], kanuri]
   krc: [Cyrl, [EU], къарачай-малкъар]
   kri: [Latn, [AF], Krio]
   krj: [Latn, [AS], Kinaray-a]

data/language-data.json

@@ -2141,7 +2141,7 @@
             [
                 "AF"
             ],
-            "Kanuri"
+            "kanuri"
         ],
         "krc": [
             "Cyrl",