Remove timestamp from test_coast_alias (#785)

Fixes the bug introduced in #769.

Author: seisman

pygmt/tests/test_coast.py

@@ -53,7 +53,6 @@ def test_coast_aliases():
         D="i",
         A=1000,
         L="jCM+c1+w1000k+f+l",
-        U=True,
         X="a4c",
         Y="a10c",
         p="135/25",
@@ -71,7 +70,6 @@ def test_coast_aliases():
         resolution="i",  # D
         area_thresh=1000,  # A
         map_scale="jCM+c1+w1000k+f+l",  # L
-        timestamp=True,  # U
         xshift="a4c",  # X
         yshift="a10c",  # Y
         perspective=[135, 25],  # p