Remove Legacy-resolver and changed constraints

Legacy-resolver will have its support dropped in the future.

Also, legacy-resolver was masking a dependency conflict that
required the constraints files be updated.  To use the
updated constraints file, the stx-integ-pylint job had to be
updated.  This update matches what is done in other repos,
eg. https://github.com/starlingx/update/blob/master/.zuul.yaml#L108.

Test Plan:
Execute: tox

Closes-Bug: 1964372

Signed-off-by: Joshua Kraitberg <joshua.kraitberg@windriver.com>
Change-Id: I6b71f0cd3d9315f957d6a6a15bf0a22e2a692185

.zuul.yaml

@@ -164,9 +164,12 @@
 # Try this as a tox-based job with a minimal functional target in tox.ini
 - job:
     name: stx-integ-pylint
-    parent: openstack-tox-pylint
+    parent: tox
     required-projects:
       - starlingx/config
+    vars:
+      tox_envlist: pylint
+      tox_extra_args: -c tox.ini
 
 - job:
     name: stx-integ-upload-git-mirror

tox.ini

@@ -5,8 +5,8 @@ skipsdist = True
 stxdir = {toxinidir}/..
 
 [testenv]
-install_command = pip install  --use-deprecated legacy-resolver  -U \
-  -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/openstack/requirements/raw/branch/stable/stein/upper-constraints.txt} \
+install_command = pip install -U \
+  -c{env:UPPER_CONSTRAINTS_FILE:https://opendev.org/starlingx/root/raw/branch/master/build-tools/requirements/debian/upper-constraints.txt} \
   {opts} {packages}
 setenv = VIRTUAL_ENV={envdir}
          OS_STDOUT_CAPTURE=1