Customization update does not delete old plugins

[msoutopico]

Pre-conditions

A version n of a plugin is in the local installation and a version n+1 is available for download. The remote _versionnotes.txt accordingly as +1 version than the local version. Eg.

Latest version in local version_notes.txt is:

## Update 51_c0p (2020-07-01)
* Blabla.

Local plugins folder has:

• plugin-omt-package-1.6.0.jar

Latest version in remote version_notes.txt is :

## Update 52_c0p (2020-07-03)
* Plugin `plugin-omt-package-1.6.1.jar` available.

Expected results

After the update, the plugins folder has (among others):

• plugin-omt-package-1.6.1.jar

Actual results

After the update, the plugins folder has (among others):

• plugin-omt-package-1.6.0.jar
• plugin-omt-package-1.6.1.jar

Further info

Reproduced by some users (e.g. IL) but not others.

[kosivantsov]

can't reproduce

[msoutopico]

Bug still reproduced with version 0.4.9 of the script (tested with OmegaT versions 4.2.0 and 5.4.0)