anim07.sh. Data registration (_g vs _p). (#8598)

* anim07.sh. Data registration (_g vs _p).

grdgradient and grdimage uses different data registration (see 
https://docs.generic-mapping-tools.org/dev/datasets/remote-data.html#data-registration).

This causes an error in this animation. 
I append  _p for grdgradient to solve it.

Approve if you think that is the best solution.

* Fix anim08 and anim11

doc/examples/anim07/anim07.sh

@@ -21,7 +21,7 @@ gmt begin
 	# Extract a topography CPT
 	gmt makecpt -Cdem2 -T0/6000 -H > z.cpt
 	# Get gradients of the relief from N45E
-	gmt grdgradient @earth_relief_06m -Nt1.2 -A45 -Gintens.grd
+	gmt grdgradient @earth_relief_06m_p -Nt1.2 -A45 -Gintens.grd
 gmt end
 EOF
 # 2. Set up main script

doc/examples/anim08/anim08.sh

@@ -38,7 +38,7 @@ gmt begin
 	2018-12-31T	240
 	EOF
     # Get gradients of the relief from N45E
-    gmt grdgradient @earth_relief_02m -Nt1.2 -A45 -Gintens.nc
+    gmt grdgradient @earth_relief_02m_p -Nt1.2 -A45 -Gintens.nc
 	gmt makecpt -Cterra -T-10000/8000 -H > t.cpt
 gmt end
 EOF

doc/examples/anim11/anim11.sh

@@ -21,7 +21,7 @@ gmt begin
   # Make global grid with a smooth 2-degree day/night transition for the 2020 solstice.
   gmt grdmath -Rd -I2m -rp $(gmt solar -C -o0:1 -I+d2020-06-20+z-10) 2 DAYNIGHT = daynight.grd
   # We will create an intensity grid based on a DEM so that we can see structures in the oceans
-  gmt grdgradient @earth_relief_02m -Nt0.75 -A45 -Gintens.grd
+  gmt grdgradient @earth_relief_02m_p -Nt0.75 -A45 -Gintens.grd
   # Make sure our remote files have been downloaded
   gmt which -Ga @earth_day_02m @earth_night_02m
 gmt end