mnit_simple: rename FDROID metadata to match the java_package

Signed-off-by: Jean Privat <jean@pryen.org>

diff --git a/examples/mnit_simple/org.nitlanguage.simple.txt b/examples/mnit_simple/org.nitlanguage.test_all.txt
similarity index 100%
rename from examples/mnit_simple/org.nitlanguage.simple.txt
rename to examples/mnit_simple/org.nitlanguage.test_all.txt