encoding/json/v2: fix typo in comment

Use the correct spelling of the Gregorian calendar.

Change-Id: I7e1d2974d38d5d3ded64f98852ee726c7b84be22
Reviewed-on: https://go-review.googlesource.com/c/go/+/704595
Reviewed-by: Joseph Tsai <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>
Auto-Submit: Emmanuel Odeke <[email protected]>

Author: mohanson

src/encoding/json/v2/arshal_time.go

@@ -465,7 +465,7 @@ func appendDurationISO8601(b []byte, d time.Duration) []byte {
 }
 
 // daysPerYear is the exact average number of days in a year according to
-// the Gregorian calender, which has an extra day each year that is
+// the Gregorian calendar, which has an extra day each year that is
 // a multiple of 4, unless it is evenly divisible by 100 but not by 400.
 // This does not take into account leap seconds, which are not deterministic.
 const daysPerYear = 365.2425