Fixed CLIPScore import in docs

[IanMaquignaz]

Fixes #1942
Updates CLIPScore docs as seen on this page: CLIPScore

Demo code incorrectly imports CLIPScore as:

from torchmetrics.multimodal import CLIPScore

This PR corrects the import to:

from torchmetrics.multimodal.clip_score import CLIPScore

---

📚 Documentation preview 📚: https://torchmetrics--1943.org.readthedocs.build/en/1943/

[codecov]

Codecov Report

Merging #1943 (68d5acf) into master (fc344c4) will decrease coverage by 50%.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #1943     +/-   ##
========================================
- Coverage      85%     35%    -50%     
========================================
  Files         263     263             
  Lines       15087   15087             
========================================
- Hits        12833    5216   -7617     
- Misses       2254    9871   +7617     

[IanMaquignaz]

All demos were copied to a script and run with torchmetrics master branch. No further errors were found.

import torch
_ = torch.manual_seed(42)
from torchmetrics.multimodal.clip_score import CLIPScore
metric = CLIPScore(model_name_or_path="openai/clip-vit-base-patch16")
score = metric(torch.randint(255, (3, 224, 224)), "a photo of a cat")
print(score.detach())
        
import torch
from torchmetrics.multimodal.clip_score import CLIPScore
metric = CLIPScore(model_name_or_path="openai/clip-vit-base-patch16")
metric.update(torch.randint(255, (3, 224, 224)), "a photo of a cat")
fig_, ax_ = metric.plot()
fig_.savefig("my_awesome_plot.png")

import torch
from torchmetrics.multimodal.clip_score import CLIPScore
metric = CLIPScore(model_name_or_path="openai/clip-vit-base-patch16")
values = [ ]
for _ in range(10):
    values.append(metric(torch.randint(255, (3, 224, 224)), "a photo of a cat"))
fig_, ax_ = metric.plot(values)
fig_.savefig("my_awesome_plot2.png")