reduce precision of VES regtest failing on Intel clang

[valsson]

Description

Changes to fix failing regtests related to #990

Target release

I would like my code to appear in release master

Type of contribution

• [ ] changes to code or doc authored by PLUMED developers, or additions of code in the core or within the default modules
• [ ] changes to a module not authored by you
• [x] new module contribution or edit of a module authored by you

Copyright

• [ ] I agree to transfer the copyright of the code I have written to the PLUMED developers or to the author of the code I am modifying.

• [x] the module I added or modified contains a COPYRIGHT file with the correct license information. Code should be released under an open source license. I also used the command cd src && ./header.sh mymodulename in order to make sure the headers of the module are correct.

Tests

• [x] I added a new regtest or modified an existing regtest to validate my changes.
• [ ] I verified that all regtests are passed successfully on GitHub Actions.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (eeff0bf) 84.12% compared to head (3265ffd) 84.12%.

:exclamation: Current head 3265ffd differs from pull request most recent head 4f593ce. Consider uploading reports for the commit 4f593ce to get more accurate results

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #994 +/- ## ======================================= Coverage 84.12% 84.12% ======================================= Files 602 602 Lines 56092 56092 ======================================= Hits 47186 47186 Misses 8906 8906 ```

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