diff-options.txt: avoid "regex" overload in example

diff-options.txt: avoid "regex" overload in example

When we exemplify the difference between `-G` and `-S` (using
`--pickaxe-regex`), we do so using an example diff and git-diff
invocation involving "regexec", "regexp", "regmatch", ...

The example is correct, but we can make it easier to untangle by
avoiding writing "regex.*" unless it's really needed to make our point.

Use some made-up, non-regexy words instead.

Reported-by: Adam Dinwoodie <redacted>
Signed-off-by: Martin Ågren <redacted>
Reviewed-by: Taylor Blau <redacted>
Signed-off-by: Junio C Hamano <redacted>