This can be done also when updating from, say, 1.7.x to 1.8.x.
Not to manually reinstall all the packages, , after installing, just create the v1.8 folder in the folder .julia/environments/ and copy the Project.toml file from the v1.7 to the v1.8 folder.
Then in a session of the new julia version run:
] instantiate
See FAQ.