Pin pip <26.0 to fix broken requirements upgrade PRs

[irtazaakram]

Description

pip==26.0 introduces a breaking change that causes requirements upgrade PRs to fail when using pip-tools. As a result, make upgrade is currently broken both locally and in CI.

This PR pins pip to <26.0 as a temporary mitigation until pip-tools releases a compatible fix.

Upstream issue tracking this breakage:
jazzband/pip-tools#2319

---

Error

pip install -qr requirements/pip-tools.txt

Notice:  A new release of pip is available: 25.3 -> 26.0
Notice:  To update, run: pip install --upgrade pip
pip install -qr requirements/pip.txt

Notice:  A new release of pip is available: 25.3 -> 26.0
Notice:  To update, run: pip install --upgrade pip
# Make sure to compile files after any other files they include!
pip-compile --upgrade  --allow-unsafe -o requirements/pip.txt requirements/pip.in
WARNING: --strip-extras is becoming the default in version 8.0.0. To silence this warning, either use --strip-extras to opt into the new default or use --no-strip-extras to retain the existing behavior.
#
# This file is autogenerated by pip-compile with Python 3.11
# by the following command:
#
#    make upgrade
#
packaging==26.0
    # via wheel
wheel==0.46.3
    # via -r requirements/pip.in

# The following packages are considered to be unsafe in a requirements file:
pip==26.0
    # via -r requirements/pip.in
setuptools==80.10.2
    # via -r requirements/pip.in
pip-compile --upgrade  -o requirements/pip-tools.txt requirements/pip-tools.in
WARNING: --strip-extras is becoming the default in version 8.0.0. To silence this warning, either use --strip-extras to opt into the new default or use --no-strip-extras to retain the existing behavior.
#
# This file is autogenerated by pip-compile with Python 3.11
# by the following command:
#
#    make upgrade
#
build==1.4.0
    # via pip-tools
click==8.3.1
    # via pip-tools
packaging==26.0
    # via
    #   build
    #   wheel
pip-tools==7.5.2
    # via -r requirements/pip-tools.in
pyproject-hooks==1.2.0
    # via
    #   build
    #   pip-tools
wheel==0.46.3
    # via pip-tools

# The following packages are considered to be unsafe in a requirements file:
# pip
# setuptools
pip install -qr requirements/pip.txt
pip install -qr requirements/pip-tools.txt
pip-compile --upgrade  -o requirements/base.txt requirements/base.in
Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.11.14/x64/bin/pip-compile", line 7, in <module>
    sys.exit(cli())
             ^^^^^
  File "/opt/hostedtoolcache/Python/3.11.14/x64/lib/python3.11/site-packages/click/core.py", line 1485, in __call__
    return self.main(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/hostedtoolcache/Python/3.11.14/x64/lib/python3.11/site-packages/click/core.py", line 1406, in main
    rv = self.invoke(ctx)
         ^^^^^^^^^^^^^^^^
  File "/opt/hostedtoolcache/Python/3.11.14/x64/lib/python3.11/site-packages/click/core.py", line 1269, in invoke
    return ctx.invoke(self.callback, **ctx.params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/hostedtoolcache/Python/3.11.14/x64/lib/python3.11/site-packages/click/core.py", line 824, in invoke
    return callback(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/hostedtoolcache/Python/3.11.14/x64/lib/python3.11/site-packages/click/decorators.py", line 34, in new_func
    return f(get_current_context(), *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/hostedtoolcache/Python/3.11.14/x64/lib/python3.11/site-packages/piptools/scripts/compile.py", line 475, in cli
    prereleases=repository.finder.allow_all_prereleases or pre,
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'PackageFinder' object has no attribute 'allow_all_prereleases'
make: *** [Makefile:28: upgrade] Error 1

[farhan]

@bmtcril Please merge this, assuming you will have rights to merge it.