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, 8 insertions, 8 deletions

diff --git a/test/tc_axlsx.rb b/test/tc_axlsx.rb
index f4f6a01d..66b12ff9 100644
--- a/test/tc_axlsx.rb
+++ b/test/tc_axlsx.rb
@@ -96,9 +96,9 @@ class TestAxlsx < Test::Unit::TestCase
   end
 
   def test_range_to_a
-    assert_equal([['A1', 'B1', 'C1']],                         Axlsx::range_to_a('A1:C1'))
-    assert_equal([['A1', 'B1', 'C1'], ['A2', 'B2', 'C2']],     Axlsx::range_to_a('A1:C2'))
-    assert_equal([['Z5', 'AA5', 'AB5'], ['Z6', 'AA6', 'AB6']], Axlsx::range_to_a('Z5:AB6'))
+    assert_equal([['A1', 'B1', 'C1']],                         Axlsx.range_to_a('A1:C1'))
+    assert_equal([['A1', 'B1', 'C1'], ['A2', 'B2', 'C2']],     Axlsx.range_to_a('A1:C2'))
+    assert_equal([['Z5', 'AA5', 'AB5'], ['Z6', 'AA6', 'AB6']], Axlsx.range_to_a('Z5:AB6'))
   end
 
   def test_sanitize_frozen_control_strippped
@@ -165,15 +165,15 @@ class TestAxlsx < Test::Unit::TestCase
   def test_escape_formulas
     Axlsx.instance_variable_set(:@escape_formulas, nil)
 
-    refute Axlsx::escape_formulas
+    refute Axlsx.escape_formulas
 
-    Axlsx::escape_formulas = true
+    Axlsx.escape_formulas = true
 
-    assert Axlsx::escape_formulas
+    assert Axlsx.escape_formulas
 
-    Axlsx::escape_formulas = false
+    Axlsx.escape_formulas = false
 
-    refute Axlsx::escape_formulas
+    refute Axlsx.escape_formulas
   ensure
     Axlsx.instance_variable_set(:@escape_formulas, nil)
   end