[7.x] Remove duplicate but in error message (#50699)

Author: azasypkin

packages/kbn-config-schema/src/types/__snapshots__/uri_type.test.ts.snap

@@ -36,7 +36,7 @@ export class URIType extends Type<string> {
       case 'string.base':
         return `expected value of type [string] but got [${typeDetect(value)}].`;
       case 'string.uriCustomScheme':
-        return `expected URI with scheme [${scheme}] but but got [${value}].`;
+        return `expected URI with scheme [${scheme}] but got [${value}].`;
       case 'string.uri':
         return `value is [${value}] but it must be a valid URI (see RFC 3986).`;
     }