Extension sphinxcontrib-htmlhelp has typo

[ukulle]

Describe the bug

class HTMLHelpBuilder in __init__.py names an incorrect file extension in the string of the variable epilog for the correct generated HTMLHelp project file .

Incorrect is the part .htp because .hhp is meant.

How to Reproduce

Code snippet:

class HTMLHelpBuilder(StandaloneHTMLBuilder):
    """
    Builder that also outputs Windows HTML help project, contents and
    index files.  Adapted from the original Doc/tools/prechm.py.
    """
    name = 'htmlhelp'
    epilog = __('You can now run HTML Help Workshop with the .htp file in '
                '%(outdir)s.')

epilog should become:

    epilog = __('You can now run HTML Help Workshop with the .hhp file in '
                '%(outdir)s.')

Environment Information

Platform:              win32; (Windows-10-10.0.19045-SP0)
Python version:        3.11.4 (tags/v3.11.4:d2340ef, Jun  7 2023, 05:45:37) [MSC v.1934 64 bit (AMD64)])
Python implementation: CPython
Sphinx version:        7.2.6
Docutils version:      0.20.1
Jinja2 version:        3.1.2
Pygments version:      2.16.1

Sphinx extensions

No response

Additional context

No response