test(e2e): spell the find negation as -not in select-e2e_test

The negated-assertion audit reads a continued line that starts with
`!` as a bash statement, so the `! -type d` operand inside the find
expression on the continuation line turned the unit lane red on main.
`-not` is the same find predicate and is not a statement prefix.

Assisted-by: LLM
Signed-off-by: Aleksei Sviridkin <f@lex.la>

hack/select-e2e_test.bats

@@ -31,7 +31,7 @@
 # expanded, but not which side is which, and reading a whole-tree diff off a trace
 # line is exactly the moment a test stops being worth having.
 full_suite_list() {
-    find hack/e2e-chainsaw -mindepth 2 \( ! -type d -o -name chainsaw-test.yaml -o -name chainsaw-test.yml \) \
+    find hack/e2e-chainsaw -mindepth 2 \( -not -type d -o -name chainsaw-test.yaml -o -name chainsaw-test.yml \) \
       | sed -nE 's,^hack/e2e-chainsaw/([^/]+)/(.*/)?(chainsaw-test|[0-9]+-[^/]*)\.ya?ml$,\1,p' \
       | sort -u | paste -sd ' ' -
 }