[tests][libFuzzer] Fix `-Wmissing-field-initializers` after D86092

Speculatively fix `-Werror,-Wmissing-field-initializers` failures
relating to the `ScalePerExecTime` field added by D86092.

GitOrigin-RevId: dde16ef031a0a9465444b0b02b9427709ef70651
1 file changed