Update the default migration template to adhere to PSR 12 formatting

[natewiebe13]

Q	A
Type	improvement
BC Break	no
Fixed issues	#1119

Summary

This change updates the generated migration file to follow the PSR-12 standard. To pull the exact phrasing:

When you have a return type declaration present, there MUST be one space after the colon followed by the type declaration. The colon and declaration MUST be on the same line as the argument list closing parenthesis with no spaces between the two characters.

This will help keep formatting consistent between the migrations and the application and removes the need to reformat the migration file after it's created.

[lcobucci]

This is following doctrine CS. We have been discussing to merge some things of psr12 there. It is better to wait until we have CS v7 to update things IMHO.

[alcaeus]

I agree. Migrating to PSR-12 is on the menu for doctrine/coding-standard. Let’s wait until that’s done 👍

[guilliamxavier]

The Doctrine CS was updated a while ago, see #1119 (comment), so this PR should be fine now

[natewiebe13]

Updated PR with changes to docs.