feat: Add OciClientV2 only, drop V1 OCI client

Remove OciClient (V1) and all V1-specific code paths, keeping only
OciClientV2. Also add oci_client.py to .fernignore alongside other
manually-maintained client files.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: fern-support

.fernignore

@@ -15,6 +15,7 @@ src/cohere/manually_maintained/__init__.py
 src/cohere/bedrock_client.py
 src/cohere/aws_client.py
 src/cohere/sagemaker_client.py
+src/cohere/oci_client.py
 src/cohere/client_v2.py
 mypy.ini
 src/cohere/aliases.py

src/cohere/__init__.py

@@ -518,7 +518,6 @@
     "NotFoundError": ".errors",
     "NotImplementedError": ".errors",
     "OAuthAuthorizeResponse": ".types",
-    "OciClient": ".oci_client",
     "OciClientV2": ".oci_client",
     "ParseInfo": ".types",
     "RerankDocument": ".types",
@@ -853,7 +852,6 @@ def __dir__():
     "NotFoundError",
     "NotImplementedError",
     "OAuthAuthorizeResponse",
-    "OciClient",
     "OciClientV2",
     "ParseInfo",
     "RerankDocument",