Fixed compilation error on Clang 10

CHANGELOG.md

@@ -7,6 +7,7 @@ HEAD
 * Made `JsonDocument`'s destructor protected (issue #1480)
 * Added missing calls to `client.stop()` in `JsonHttpClient.ino` (issue #1485)
 * Fixed error `expected ')' before 'char'` when `isdigit()` is a macro (issue #1487)
+* Fixed error `definition of implicit copy constructor is deprecated` on Clang 10
 
 v6.17.2 (2020-11-14)
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