tests: rename file to lowercase

Thanks to autocomplete i didn't notice this earlier,
make this lowercase.

Signed-off-by: Florian Westphal <fw@strlen.de>

diff --git a/tests/shell/testcases/bogons/nft-f/mapping_With_invalid_datatype_crash b/tests/shell/testcases/bogons/nft-f/mapping_with_invalid_datatype_crash
similarity index 100%
rename from tests/shell/testcases/bogons/nft-f/mapping_With_invalid_datatype_crash
rename to tests/shell/testcases/bogons/nft-f/mapping_with_invalid_datatype_crash