Use consistent indentation in src/sass/_theme_rst.sass (#1234)

Author: mitya57

src/sass/_theme_rst.sass

@@ -106,11 +106,11 @@
       pointer-events: none
 
     span.linenos
-     display: inline-block
-     padding-left: 0px
-     padding-right: ($base-line-height / 2)
-     margin-right: ($base-line-height / 2)
-     border-right: 1px solid lighten($table-border-color, 2%)
+      display: inline-block
+      padding-left: 0px
+      padding-right: ($base-line-height / 2)
+      margin-right: ($base-line-height / 2)
+      border-right: 1px solid lighten($table-border-color, 2%)
 
   .code-block-caption
     font-style: italic