meta-selftest/files: add ptest to static-passwd/-group

As ptest-runner creates a new user, we need to add it to the testing
static passwd file.

(From OE-Core rev: 009726f04c000cc50ce44305669bd8e940e64a9c)

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-selftest/files/static-group

@@ -25,3 +25,4 @@ weston:x:525:
 wayland:x:526:
 render:x:527:
 sgx:x:528:
+ptest:x:529:

meta-selftest/files/static-passwd

@@ -17,3 +17,4 @@ bind:x:521:521::/:/bin/nologin
 builder:x:522:522::/:/bin/nologin
 _apt:x:523:523::/:/bin/nologin
 weston:x:525:525::/:/bin/nologin
+ptest:x:529:529::/:/bin/nologin