Feat: add gutter and remove margin (#375)

* fix: the margin and gutter

* fix: the extra line

* fix: the extra line

* fix: the extra line from examples

* fix: the extra line from userguide

Author: Revathyvenugopal162

doc/source/api.rst

@@ -19,6 +19,7 @@ PyAnsys packages API reference
 ******************************
 
 .. grid:: 3
+    :gutter: 3 3 4 4
 
     .. grid-item-card:: PyAEDT
       :img-top: _static/thumbnails/pyaedt.png

doc/source/examples.rst

@@ -8,6 +8,7 @@ PyAnsys packages examples
 *************************
 
 .. grid:: 3
+    :gutter: 3 3 4 4
 
     .. grid-item-card:: PyAEDT
       :img-top: _static/thumbnails/pyaedt.png