Fix safe Style/ColonMethodCall offenses

Caxlsx is using both `.` and `::`, 220 occurrences vs 280 to invoke
methods on `Axlsx` module.

This commit standardizes the approach towards `.`, which will also allow
shorter lines.

Performance is not affected

```
Comparison:
      Axlsx.validate:  8515252.3 i/s
     Axlsx::validate:  8512863.7 i/s - same-ish: difference falls within error 
```

1 files changed, 5 insertions, 5 deletions

diff --git a/lib/axlsx/drawing/marker.rb b/lib/axlsx/drawing/marker.rb
index a1801eb9..ec476297 100644
--- a/lib/axlsx/drawing/marker.rb
+++ b/lib/axlsx/drawing/marker.rb
@@ -34,13 +34,13 @@ module Axlsx
     attr_reader :rowOff
 
     # @see col
-    def col=(v) Axlsx::validate_unsigned_int v; @col = v end
+    def col=(v) Axlsx.validate_unsigned_int v; @col = v end
     # @see colOff
-    def colOff=(v) Axlsx::validate_int v; @colOff = v end
+    def colOff=(v) Axlsx.validate_int v; @colOff = v end
     # @see row
-    def row=(v) Axlsx::validate_unsigned_int v; @row = v end
+    def row=(v) Axlsx.validate_unsigned_int v; @row = v end
     # @see rowOff
-    def rowOff=(v) Axlsx::validate_int v; @rowOff = v end
+    def rowOff=(v) Axlsx.validate_int v; @rowOff = v end
 
     # shortcut to set the column, row position for this marker
     # @param col the column for the marker, a Cell object or a string reference like "B7"
@@ -68,7 +68,7 @@ module Axlsx
     # @see Chart#start_at
     def parse_coord_args(x, y = 0)
       if x.is_a?(String)
-        x, y = *Axlsx::name_to_indices(x)
+        x, y = *Axlsx.name_to_indices(x)
       end
       if x.is_a?(Cell)
         x, y = *x.pos