Fix Style/HashEachMethods offense

Replace `keys.each` with hash iteration

```rb
MY_HASH = {
  first: '1',
  second: '2',
  third: '3'
}

%i[ips memory].each do |benchmark|
  Benchmark.send(benchmark) do |x|
    x.report("each_key") { MY_HASH.each_key { |k| MY_HASH[k] } }
    x.report("keys.each") { MY_HASH.keys.each { |k| MY_HASH[k] } }
    x.report("each") { MY_HASH.each { |k, v| v } }
    x.compare!
  end
end
```

```
IPS Comparison:
                each:  4283031.6 i/s
            each_key:  3683407.4 i/s - 1.16x  (± 0.00) slower
           keys.each:  3387425.1 i/s - 1.26x  (± 0.00) slower

Memory Comparison:
            each_key:          0 allocated
                each:          0 allocated - same
           keys.each:         40 allocated - Infx more
```

1 files changed, 3 insertions, 3 deletions

diff --git a/lib/axlsx/workbook/worksheet/rich_text_run.rb b/lib/axlsx/workbook/worksheet/rich_text_run.rb
index ffd2f941..e3522d4c 100644
--- a/lib/axlsx/workbook/worksheet/rich_text_run.rb
+++ b/lib/axlsx/workbook/worksheet/rich_text_run.rb
@@ -211,14 +211,14 @@ module Axlsx
       data = data.select { |key, value| valid.include?(key) && !value.nil? }
 
       str << '<r><rPr>'
-      data.keys.each do |key|
+      data.each do |key, val|
         case key
         when :font_name
           str << '<rFont val="' << font_name << '"/>'
         when :color
-          str << data[key].to_xml_string
+          str << val.to_xml_string
         else
-          str << '<' << key.to_s << ' val="' << xml_value(data[key]) << '"/>'
+          str << '<' << key.to_s << ' val="' << xml_value(val) << '"/>'
         end
       end
       clean_value = Axlsx::trust_input ? @value.to_s : ::CGI.escapeHTML(Axlsx::sanitize(@value.to_s))