Fix: Remove duplicate RELEASE_BUILD default assignment (was overwriting ON to OFF)

- Line 1327 had RELEASE_BUILD="${RELEASE_BUILD:-OFF}" which overwrote
  the correct default at line 745 (RELEASE_BUILD="${RELEASE_BUILD:-ON}")
- This caused release scope builds to incorrectly build all modules
  instead of just TetraIF, Z, and Lts/Common
- Removed the duplicate assignment to preserve the ON default

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

qt6-after/qt6-migrated-legatus/new_docker_build.sh

@@ -1324,7 +1324,7 @@ BUILD_TAG="${BUILD_TAG:-manual-build}"
 BUILD_CODIFICATION="${BUILD_CODIFICATION:-OFF}"
 VERIFY_RPM="${VERIFY_RPM:-OFF}"
 CMAKE_BUILD_FLAGS="${CMAKE_BUILD_FLAGS:-}"
-RELEASE_BUILD="${RELEASE_BUILD:-OFF}"
+# RELEASE_BUILD already set above at line 745 - don't overwrite
 QT_VERSION="${QT_VERSION:-6.10.2}"
 QT_ARCH="${QT_ARCH:-linux_gcc_64}"
 QT_ARCH_DIR="${QT_ARCH_DIR:-gcc_64}"