free_botswana and Lourenco Marques fixes

[cetvrtak]

1. Free Botswana decision - release_vassal = TSW requires them to be a vassal already to release from that status. Use release = TSW create_vassal = TSW

2. Getting Lourenço Marques event - although not an error, it would be better to scope to the state from a province already checked in the trigger - 2049 or 2050 instead of 2051

[moretrim]

1. Free Botswana decision - release_vassal = TSW requires them to be a vassal already to release from that status. Use release = TSW create_vassal = TSW

release_vassal has two functions:

• it makes the non-existing argument country appear on the map, as if the country in scope had used the “Release Nation” button of the politics screen (it’s close enough anyway)
• it breaks the vassal–puppet bond of the already existing argument country

Looking at the decision requirements it looks to me that the first role is intended here:

https://github.com/arkhometha/Historical-Project-Mod/blob/a181b6c01ed76b460bb4a21cb2cedc4aa0c35836/HPM/decisions/New%20Colonies.txt#L7280

This seems entirely appropriate for creating a colonial puppet to me.

In contrast, release makes the argument country undergo the same process as during loading a new campaign, by reading from the history files.