tests/basics: Add .exp file for sys.tracebacklimit test.

The sys.tracebacklimit feature has changed semantics a bit from CPython 3.7
(in the way it modifies the output), so provide a .exp file for the test so
it doesn't rely on CPython.
Signed-off-by: Damien George <damien@micropython.org>

tests/basics/sys_tracebacklimit.py.exp

+Traceback (most recent call last):
+  File  , line 62, in ftop
+  File  , line 57, in f3
+  File  , line 53, in f2
+  File  , line 49, in f1
+  File  , line 45, in f0
+ValueError: value
+
+limit 4
+Traceback (most recent call last):
+  File  , line 62, in ftop
+  File  , line 57, in f3
+  File  , line 53, in f2
+  File  , line 49, in f1
+ValueError: value
+
+limit 3
+Traceback (most recent call last):
+  File  , line 62, in ftop
+  File  , line 57, in f3
+  File  , line 53, in f2
+ValueError: value
+
+limit 2
+Traceback (most recent call last):
+  File  , line 62, in ftop
+  File  , line 57, in f3
+ValueError: value
+
+limit 1
+Traceback (most recent call last):
+  File  , line 62, in ftop
+ValueError: value
+
+limit 0
+ValueError: value
+
+limit -1
+ValueError: value
+
+True
+False