Fix find-package example uninstall executable name

[dajiaohuang]

Problem

The find-package example builds and installs exprog3, but its uninstall target removes exprog2. After configuring, building and installing the example, cmake --build <build-dir> --target uninstall succeeds while leaving the installed bin/exprog3 in place. It can also remove an unrelated bin/exprog2 in the same prefix.

Change

Use exprog3 in the removal path, matching the executable and install target. No library behavior changes.

Validation

Using CMake and GCC 13.3 on Ubuntu 24.04, with an isolated temporary installation prefix:

• Built and installed rapidcsv, then configured/built the actual find-package example against that installation.
• Before the change, uninstall left exprog3 behind.
• After the change, uninstall removed exprog3 and preserved a synthetic neighboring exprog2 file.
• The example executable still runs successfully.
• git diff --check passes.

Windows/macOS install layouts were not tested.