fix: kwargs.pop("redis_url") KeyError: 'redis_url' (#3121)

This occurred when redis_url was not passed as a parameter even though a
REDIS_URL env variable was present.
This occurred for all methods that eventually called any of:
(from_texts, drop_index, from_existing_index) - i.e. virtually all
methods in the class.
This fixes it

langchain/vectorstores/redis.py

@@ -273,6 +273,7 @@ class Redis(VectorStore):
         try:
             # We need to first remove redis_url from kwargs,
             # otherwise passing it to Redis will result in an error.
+            if "redis_url" in kwargs:
                 kwargs.pop("redis_url")
             client = redis.from_url(url=redis_url, **kwargs)
             # check if redis has redisearch module installed
@@ -365,6 +366,7 @@ class Redis(VectorStore):
         try:
             # We need to first remove redis_url from kwargs,
             # otherwise passing it to Redis will result in an error.
+            if "redis_url" in kwargs:
                 kwargs.pop("redis_url")
             client = redis.from_url(url=redis_url, **kwargs)
         except ValueError as e:
@@ -400,6 +402,7 @@ class Redis(VectorStore):
         try:
             # We need to first remove redis_url from kwargs,
             # otherwise passing it to Redis will result in an error.
+            if "redis_url" in kwargs:
                 kwargs.pop("redis_url")
             client = redis.from_url(url=redis_url, **kwargs)
             # check if redis has redisearch module installed