Update style-guide.adoc with 4 proper rendering of "`" character

[fanofxiaofeng]

As mentioned in Example 6 in https://docs.asciidoctor.org/asciidoc/latest/syntax-quick-reference/#text-formatting,
two consecutive "`" character can be used to render unconstrained italic (I think it means italic that are not constrained to boundary of words)

There are four places that "`" is not rendered as expected in this adoc file (as shown above), I tried to fix all of them.
Please help review. Thanks

[paulk-asert]

Thanks for spotting those. I suspect they might have worked as is on a very old version of Asciidoc. In any case, I think the sentence could be made clearer without the pluralization of those keywords. I might try to reword if I can find time.

[fanofxiaofeng]

OK, thanks for the details.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.6608%. Comparing base (6cd477b) to head (31bcef4).
Report is 329 commits behind head on master.

Additional details and impacted files

@@                Coverage Diff                 @@
##               master      #2119        +/-   ##
==================================================
+ Coverage     68.5957%   68.6608%   +0.0651%     
- Complexity      29233      29416       +183     
==================================================
  Files            1426       1427         +1     
  Lines          113494     113631       +137     
  Branches        19548      19634        +86     
==================================================
+ Hits            77852      78020       +168     
+ Misses          29088      29047        -41     
- Partials         6554       6564        +10     

see 94 files with indirect coverage changes