fix: skip French locale test when locale unavailable (#1213)

[LeonidasZhak]

Problem

Test "parsing months with dots works in French linux locale" (test-parsers.R:1121) errors on systems where fr_FR.utf8 is not installed:

Error in `Sys.setlocale("LC_TIME", locale)`: (converted from warning) OS reports request to set locale to "fr_FR.utf8" cannot be honored

Fix

Added skip_if guard and on.exit cleanup, matching the existing pattern in the adjacent test "parsing with r and R formats works in non-english locale" (line 1143):

suppressWarnings(testthat::skip_if(Sys.setlocale("LC_TIME", "fr_FR.utf8") == ""))
on.exit(Sys.setlocale("LC_TIME", "C"))

Testing

• Ran testthat::test_file("tests/testthat/test-parsers.R") — all tests pass
• On macOS: test skipped via skip_on_os("mac") (pre-existing)
• On Linux without French locale: now gracefully skipped via skip_if (the fix)

Closes #1213

[vspinu]

Thanks!