UTC_OFFSET_FORMAT: use const blocks around function calls #1723

Job	Run time
Clippy	44s
Type-check benchmarks	16s
Coverage	31s
Type checking (MSRV, no_std)	3m 59s
Cross-build	32s
Type checking (MSRV, std_no_offset)	5m 41s
Documentation	17s
Formatting	12s
Type checking (MSRV, std_with_offset)	4m 24s
Type checking (stable, no_std)	43s
Test (miri)	14m 54s
Type checking (stable, std_no_offset)	2m 16s
Test (Ubuntu, MSRV)	3m 56s
Type checking (stable, std_with_offset)	1m 20s
Test (Windows, MSRV)	5m 11s
Test (MacOS, MSRV)	3m 23s
Test (Ubuntu, stable)	41s
Test (Windows, stable)	2m 44s
Test (MacOS, stable)	40s
Publish docs	0s
	52m 24s

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