Remove and add cloud back to allowed_clouds will cause the cloud be excluded in plan

[aylei]

repro:

# 1. Preview result with 7 clouds
$ cat ~/.sky/config.yaml
allowed_clouds:
  - aws
  - gcp
  - azure
  - kubernetes
  - runpod
  - cudo
  - paperspace
$ sky launch --gpus H100:8
Considered resources (1 node):
-------------------------------------------------------------------------------------------------------
 CLOUD        INSTANCE         vCPUs   Mem(GB)   ACCELERATORS   REGION/ZONE        COST ($)   CHOSEN
-------------------------------------------------------------------------------------------------------
 RunPod       8x_H100_SECURE   128     640       H100:8         CA                 35.92         ✔
 Paperspace   H100x8           128     640       H100:8         East Coast (NY2)   47.60
 GCP          a3-highgpu-8g    208     1872      H100:8         us-central1-a      87.83
 AWS          p5.48xlarge      192     2048      H100:8         us-east-1          98.32
-------------------------------------------------------------------------------------------------------
Launching a new cluster 'sky-e1a9-aylei'. Proceed? [Y/n]: ^CAborted!

# 2. Remove `aws` and `gcp` from allowed_clouds, the plan works as expected
$ sky launch --gpus H100:8
Considered resources (1 node):
-------------------------------------------------------------------------------------------------------
 CLOUD        INSTANCE         vCPUs   Mem(GB)   ACCELERATORS   REGION/ZONE        COST ($)   CHOSEN
-------------------------------------------------------------------------------------------------------
 RunPod       8x_H100_SECURE   128     640       H100:8         CA                 35.92         ✔
 Paperspace   H100x8           128     640       H100:8         East Coast (NY2)   47.60
-------------------------------------------------------------------------------------------------------
Launching a new cluster 'sky-7805-aylei'. Proceed? [Y/n]: ^CAborted!

# 3. Add `aws` and `gcp` back, the plan still missing aws and gcp
$ sky launch --gpus H100:8
Considered resources (1 node):
-------------------------------------------------------------------------------------------------------
 CLOUD        INSTANCE         vCPUs   Mem(GB)   ACCELERATORS   REGION/ZONE        COST ($)   CHOSEN
-------------------------------------------------------------------------------------------------------
 RunPod       8x_H100_SECURE   128     640       H100:8         CA                 35.92         ✔
 Paperspace   H100x8           128     640       H100:8         East Coast (NY2)   47.60
-------------------------------------------------------------------------------------------------------
Launching a new cluster 'sky-b63b-aylei'. Proceed? [Y/n]: ^CAborted!

As a workaround, running sky check can fix the error.

Version & Commit info:

• sky -v: skypilot, version 1.0.0-dev0
• sky -c: skypilot, commit dad3a65