use getenv instead of accessing environ obj (#147)

I had problems importing the package after manipulating the environ
object, so the "default" keyword argument was not available anymore. In
this case getenv will still work.
The module using getenv in all other occurences, so it also good to keep
it consistent.

Co-authored-by: Jennifer Hamon <jhamon@pinecone.io>

Author: tomcsojn

pinecone/core/utils/constants.py

@@ -12,7 +12,7 @@
 
 MAX_MSG_SIZE = 128 * 1024 * 1024
 
-MAX_ID_LENGTH = int(os.environ.get("PINECONE_MAX_ID_LENGTH", default="64"))
+MAX_ID_LENGTH = int(os.getenv("PINECONE_MAX_ID_LENGTH", default="64"))
 
 REQUEST_ID: str = "request_id"
 CLIENT_VERSION_HEADER = 'X-Pinecone-Client-Version'