Fix hours of operation figures in documentation

[amylebar]

Pull request overview

• Replace start_time.png and duration.png with updated figures

Pull Request Author

This pull request makes changes to (select all the apply):

• Documentation
• Infrastructure (includes singularity image, buildstock batch, dependencies, continuous integration tests)
• Sampling
• Workflow Measures
• Upgrade Measures
• Reporting Measures
• Postprocessing

Author pull request checklist:

• Tagged the pull request with the appropriate label (documentation, infrastructure, sampling, workflow measure, upgrade measure, reporting measure, postprocessing) to help categorize changes in the release notes.
• Added tests for new measures
• Updated measure .xml(s)
• Register values added to comstock_column_definitions.csv
• Both options_lookup.tsv files updated
• 10k+ test run
• Change documentation written
• Measure documentation written
• ComStock documentation updated
• Changes reflected in example .yml files
• Changes reflected in README.md files
• Added 'See ComStock License' language to first two lines of each code file
• Implements corresponding measure tests and indexing path in test/measure_tests.txt or/and test/resource_measure_tests.txt
• All new and existing tests pass the CI

Review Checklist

This will not be exhaustively relevant to every PR.

• Perform a code review on GitHub
• All related changes have been implemented: data and method additions, changes, tests
• If fixing a defect, verify by running develop branch and reproducing defect, then running PR and reproducing fix
• Reviewed change documentation
• Ensured code files contain License reference
• Results differences are reasonable
• Make sure the newly added measures has been added with tests and indexed properly
• CI status: all tests pass

ComStock Licensing Language - Add to Beginning of Each Code File

# ComStock™, Copyright (c) 2023 Alliance for Sustainable Energy, LLC. All rights reserved.
# See top level LICENSE.txt file for license terms.