Fix five alt image text references erroneously interpreted as substitution directives in sphinx build

[speediedan]

The notebook update PR on the main repo currently has the build-docs job failing due to sphinx interpreting some alternate image text with an underscore as a substitution. This PR simply replaces underscores in those five alt image text references with hyphens to allow the build-docs workflow to proceed without error.

• Was this discussed/approved via a Github issue? (no need for typos and docs improvements)
• Did you make sure to update the docs?
• Did you write any new necessary tests?

What does this PR do?

This PR is a small doc fix replacing 5 alt image text strings that had underscores with hyphens to prevent them from being interpreted as substitution directives

PR review

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[codecov]

Codecov Report

Merging #180 (5c6023b) into main (dcf7793) will not change coverage.
The diff coverage is n/a.

@@         Coverage Diff         @@
##           main   #180   +/-   ##
===================================
  Coverage    75%    75%           
===================================
  Files         2      2           
  Lines       370    370           
===================================
  Hits        276    276           
  Misses       94     94