Prior to this commit, the PDF version of the Spring Reference Manual
contained HTML <strong></strong> tags in code examples due to the fact
that Asciidoctor converts bold formatting (i.e., elements wrapped in
`**` or `*`) within source code blocks into HTML tags even for PDF
rendering.
This commit addresses this issue by removing all bold formatting from
example code blocks.
Closes gh-22577
8f7b118701