ci: Bump minmimum version 3.6 -> 3.7, remove 3.6 classifiers

Author: tony

README.md

@@ -174,7 +174,7 @@ See donation options at <https://git-pull.com/support.html>.
 # Project details
 
 - tmux support: 1.8, 1.9a, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6
-- python support: >= 3.6, pypy, pypy3
+- python support: >= 3.7, pypy, pypy3
 - Source: <https://github.com/tmux-python/libtmux>
 - Docs: <https://libtmux.git-pull.com>
 - API: <https://libtmux.git-pull.com/api.html>

poetry.lock

@@ -15,7 +15,6 @@ classifiers = [
   "Environment :: Web Environment",
   "Intended Audience :: Developers",
   "Programming Language :: Python",
-  "Programming Language :: Python :: 3.6",
   "Programming Language :: Python :: 3.7",
   "Programming Language :: Python :: 3.8",
   "Programming Language :: Python :: 3.9",
@@ -34,7 +33,7 @@ Documentation = "https://libtmux.git-pull.com"
 Repository = "https://github.com/tmux-python/libtmux"
 
 [tool.poetry.dependencies]
-python = "^3.6"
+python = "^3.7"
 
 [tool.poetry.dev-dependencies]
 ### Docs ###
@@ -55,7 +54,7 @@ coverage = "*"
 pytest-cov = "*"
 
 ### Format ###
-black = {version="==21.9b0", python="^3.6.2"}
+black = {version="==21.9b0"}
 isort = "*"
 
 ### Lint ###

pyproject.toml

@@ -54,7 +54,6 @@
         "Environment :: Web Environment",
         "Intended Audience :: Developers",
         "Programming Language :: Python",
-        "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
         "Programming Language :: Python :: 3.9",