(MINOR) Update num_enum requirement from 0.6.0 to 0.7.0 #543

Job	Run time
Unit tests with minimum versions of direct dependencies (windows-latest)	3m 49s
Unit tests with minimum versions of direct dependencies (macos-latest)	5m 27s
Unit tests with minimum versions of direct dependencies (ubuntu-latest)	3m 10s
Unit tests with default features disabled (windows-latest, stable)	5m 21s
Unit tests with default features disabled (macos-latest, stable)	3m 40s
Unit tests with default features disabled (ubuntu-latest, stable)	2m 1s
Preflight docs.rs build	38s
Clippy	1m 42s
Enforce Rust code format	17s
License / vulnerability audit (advisories)	25s
License / vulnerability audit (bans licenses sources)	28s
Preflight crate publish (ubuntu-latest, stable)	23s
ReadXMP example	1m 44s
Unit tests (aarch64-unknown-linux-gnu, stable)	2m 48s
Unit tests (aarch64-unknown-linux-gnu, 1.64.0)	5m 59s
Unit tests (windows-latest, stable)	4m 30s
Unit tests (windows-latest, 1.64.0)	5m 25s
Unit tests (macos-latest, stable)	4m 8s
Unit tests (macos-latest, 1.64.0)	8m 46s
Unit tests (ubuntu-latest, stable)	2m 19s
Unit tests (ubuntu-latest, 1.64.0)	4m 48s
Check for unknown features in cfg attributes and macros	1m 51s
Check for unused dependencies	1m 51s
Ensure (MAJOR) tag is used when making an API breaking change	7m 11s
	1h 18m 41s

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