Make --version output valid YAML for parsing #2856

[KevinJi22]

This commit adds a colon so instead of getting

$ ./scancode --version
ScanCode version 30.1.0
ScanCode Output Format version 2.0.0
SPDX License list version 3.15

we get

$ ./scancode --version
ScanCode version: 30.1.0
ScanCode Output Format version: 2.0.0
SPDX License list version: 3.15

This will make the output easier to parse since it is valid YAML now. Fixes #2856

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[pombredanne]

Thanks!
Could you add a small test to validate that this function returns valid YAML that can be parsed?

[pombredanne]

pytest-dev/pytest#9608 is likely the cause for the failures

[pombredanne]

LGTM!