Tox/Zuul: Docs: Resolve dependency conflict

The api-ref tox job was using the constraints file
set for runtime tests (the one for the debian bullseye node).
However, doc jobs run on the default zuul node,
which currently is ubuntu noble. Due to this,
all doc jobs needed their install deps command changed.

Test Plan:
In a ubuntu noble container, install python3-venv
and bindep.txt deps. Create a venv and install tox. Run:
  pass: tox -eapi-ref
  pass: tox -ereleasenotes
  pass: tox -edocs
  pass: tox -enewnote

Partial-Bug: 2085550

Change-Id: Idef0fa628dab2d1f97c397b4a0234f6e66e0537d
Signed-off-by: Leonardo Fagundes Luz Serrano <Leonardo.FagundesLuzSerrano@windriver.com>

tox.ini

@@ -190,6 +190,7 @@ commands = {[testenv]commands}
 
 [testenv:docs]
 basepython = python3
+install_command = pip install -U {opts} {packages}
 deps = -r{toxinidir}/doc/requirements.txt
 commands =
     rm -rf doc/build
@@ -198,6 +199,7 @@ allowlist_externals = rm
 
 [testenv:releasenotes]
 basepython = python3
+install_command = pip install -U {opts} {packages}
 deps = -r{toxinidir}/doc/requirements.txt
 commands =
     rm -rf releasenotes/build
@@ -210,11 +212,13 @@ allowlist_externals =
 basepython = python3
 # Re-use the releasenotes venv
 envdir = {toxworkdir}/releasenotes
+install_command = pip install -U {opts} {packages}
 deps = -r{toxinidir}/doc/requirements.txt
 commands = reno new {posargs}
 
 [testenv:api-ref]
 basepython = python3
+install_command = pip install -U {opts} {packages}
 deps =
     -r{toxinidir}/doc/requirements.txt
 commands =