strptime/1 ignores ISO-8601 TimeZone (format string "%z")

```
~ uname -a | awk '$2 = "REDACTED"'
Linux REDACTED 4.9.0-13-amd64 #1 SMP Debian 4.9.228-1 (2020-07-05) x86_64 GNU/Linux

~ jq/jq --version
jq-1.6-128-ga17dd32-dirty

~ jq/jq -nc \
' "2020-10-15T17:30:00-0400"
, "2020-10-15T17:30:00+0000"
| strptime("%FT%T%z")
'
[2020,9,15,17,30,0,4,288]
[2020,9,15,17,30,0,4,288]
```