Update dev-requirements pip-tools

This patch updates the pip-tools version to prevent the bug when
trying to run make update-requirements failing.

dev-requirements.txt

@@ -18,12 +18,14 @@ autoflake==1.4
     # via gray
 babel==2.9.1
     # via sphinx
-backports.entry-points-selectable==1.1.0
+backports-entry-points-selectable==1.1.0
     # via virtualenv
 black==21.7b0
     # via gray
 bleach==4.1.0
     # via readme-renderer
+build==0.9.0
+    # via pip-tools
 certifi==2021.5.30
     # via requests
 cfgv==3.3.1
@@ -108,16 +110,17 @@ nodeenv==1.6.0
 packaging==21.0
     # via
     #   bleach
+    #   build
     #   pytest
     #   sphinx
     #   tox
 pathspec==0.9.0
     # via black
 pep517==0.11.0
-    # via pip-tools
+    # via build
 pep8-naming==0.12.1
     # via -r dev-requirements.in
-pip-tools==6.2.0
+pip-tools==6.9.0
     # via -r dev-requirements.in
 pkginfo==1.7.1
     # via twine
@@ -214,6 +217,7 @@ toml==0.10.2
 tomli==1.2.1
     # via
     #   black
+    #   build
     #   pep517
 tox==3.24.3
     # via -r dev-requirements.in