ci: limit fetch product types action PR body length

[sbrunato]

Truncated PR body to avoid error in Fetch providers for new product types github action:

Error: An error occurred trying to start process '/home/runner/runners/2.304.0/externals/node16/bin/node' with working directory '/home/runner/work/eodag/eodag'. Argument list too long

See peter-evans/create-or-update-comment#96 and robburger/terraform-pr-commenter#6 (comment)

[github-actions]

Test Results

       4 files  ±0         4 suites  ±0   4m 11s ⏱️ -28s
   387 tests ±0     385 ✔️ ±0    2 💤 ±0  0 ❌ ±0 
1 548 runs  ±0  1 492 ✔️ ±0  56 💤 ±0  0 ❌ ±0 

Results for commit a9a107c. ± Comparison against base commit 4c373fd.

♻️ This comment has been updated with latest results.

[github-actions]

Code Coverage (Ubuntu)

File	Coverage
All files	82%	✅

Minimum allowed coverage is 70%

Generated by 🐒 cobertura-action against a9a107c

[github-actions]

Code Coverage (Windows)

File	Coverage
All files	76%	✅

Minimum allowed coverage is 70%

Generated by 🐒 cobertura-action against a9a107c