Remove legacy `<span>` tags used for inline styling in documentation

[travisamartin]

Description

We need to remove <span> tags used for inline styling in the NGINX documentation. These tags were originally introduced when WordPress was used to publish docs, but they are no longer necessary now that we apply styles via CSS.

Problem

Inline <span> tags with style attributes (e.g., style="color:#666666; font-weight:bolder; white-space: nowrap;") are still present in many places. This introduces unnecessary complexity, makes maintenance harder, and creates inconsistencies in formatting across the docs.

Example

Current HTML:

Solution

• Remove all inline <span> tags used solely for styling.
• Replace them with Markdown formatting:
  • **bold** for UI labels and key terms
  • `inline code` for values
  • _italics_ if stylistically necessary

Rationale

• Reduces maintenance overhead by eliminating inline style overrides
• Simplifies content editing and review by using plain Markdown
• Improves readability of source files in version control
• Aligns with our current documentation standards and publishing system
• Promotes visual and structural consistency across all docs

Priority

Medium – Not urgent, but important for long-term maintainability, content quality, and consistency.

[travisamartin]

Done