DEVELOPER.md: update procedure for upgrading TZDB

DEVELOPER.md

@@ -839,7 +839,6 @@ available.
  - `HinnantBasicTest/Makefile`
  - `HinnantExtendedTest/Makefile`
  - Validate against one library, acetimec:
- - `$ vi AcetimecExtendedTest/Makefile`
  - `$ make -C AcetimecExtendedTest clean`
  - `$ make -C AcetimecExtendedTest all`
  - `$ make -C AcetimecExtendedTest run`
@@ -853,13 +852,18 @@ available.
  - Update the `TZ_VERSION` variable in the makefiles.
  - `$ make zonedbs`
 - Update CHANGELOGs
+ - Copy a summary of the TZDB release notes from
+ https://mm.icann.org/pipermail/tz-announce/ to the various CHANGELOG.md
+ files.
  - AceTime/CHANGELOG.md
  - acetimec/CHANGELOG.md
  - acetimepy/CHANGELOG.md
  - AceTimeValidation/CHANGELOG.md
-- Commit the changes to git
+- Commit and push the changes for the following repos: AceTime, acetimec,
+ acetimepy, AceTimeValidation
  - `$ git add ...`
  - `$ git commit -m "..."`
+ - `$ git push`
 
 There are 12 other validation tests in the AceTimeValidation project that
 compare AceTime with various other third party libraries: