maint: update minimum version requirement (#200)

## Which problem is this PR solving?

Python 3.7 support was dropped upstream in February, see
open-telemetry/opentelemetry-python#3668

---------

Signed-off-by: Alex Boten <[email protected]>

Author: codeboten

README.md

@@ -15,7 +15,7 @@ Latest release built with:
 
 ## Requirements
 
-- Python 3.7 or higher
+- Python 3.8 or higher
 
 ## Getting Started
 

poetry.lock

@@ -11,7 +11,6 @@ classifiers = [
     "Intended Audience :: Developers",
     "License :: OSI Approved :: Apache Software License",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.7",
     "Programming Language :: Python :: 3.8",
     "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
@@ -20,7 +19,7 @@ classifiers = [
 ]
 
 [tool.poetry.dependencies]
-python = "^3.7, >= 3.7.2"
+python = "^3.8"
 opentelemetry-api = "^1.22.0"
 opentelemetry-sdk = "^1.22.0"
 opentelemetry-exporter-otlp = "^1.22.0"