Remove the variable GMT_SHAREDIR from CI settings (#437)

The variable GMT_SHAREDIR was needed due to a GMT bug.
See GenericMappingTools/gmt#3353 for the bug report,
and GenericMappingTools/gmt#3361 for the fix.

The conda GMT package was rebuilt in conda-forge/gmt-feedstock#94,
in which the patch was applied to GMT 6.0.0.

Now PyGMT should work well with no need to add the variable GMT_SHAREDIR.

Author: seisman

.azure-pipelines.yml

@@ -165,8 +165,6 @@ jobs:
     CONDA_INSTALL_EXTRA: "codecov gmt=6.0.0"
     # ctypes.CDLL cannot find conda's libraries
     GMT_LIBRARY_PATH: 'C:\Miniconda\envs\testing\Library\bin'
-    # Due to potential bug in GMT, we have to set GMT_SHAREDIR manually
-    GMT_SHAREDIR: 'C:\Miniconda\envs\testing\Library\share\gmt'
 
   strategy:
     matrix: