Fixed typo of "projecton" to "projection" in subplot module (#1214)

Author: mdtanker

pygmt/src/subplot.py

@@ -22,7 +22,7 @@
     A="autolabel",
     B="frame",
     C="clearance",
-    J="projecton",
+    J="projection",
     M="margins",
     R="region",
     SC="sharex",