python3-twisted: prepend split PACKAGES

Fixes an issue where split packages were no populated since all the files
were picked up by FILES:${PN}

Signed-off-by: Guðni Már Gilbert <gudnimar@noxmedical.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-python/recipes-devtools/python/python3-twisted_24.3.0.bb

@@ -15,7 +15,7 @@ do_install:append() {
     find ${D} \( -name "*.bat" -o -name "*.c" -o -name "*.h" \) -exec rm -f {} \;
 }
 
-PACKAGES += "\
+PACKAGES =+ "\
     ${PN}-zsh \
     ${PN}-test \
     ${PN}-protocols \