devel/gitflow: Update to 1.12.3

• Remove patch "patch-git-flow-init" that is no longer required. [1]

While I'm here:

• Group USES block with related USE_ variables and move OPTIONS_DEFINE further down according to the PHB.

Changelog since 1.12.1:

• Explicitly get the default values from the system and global config
• Fix missing parentheses [1]

PR: 240577
Submitted by: nbari@tequila.io (maintainer)