Script to generate the contributor list has incorrect documentation

[Kyle-Ye]

In generate-contributors-list.sh file, it is suggesting we run ./scripts/generate-contributors-list.sh to update CONTRIBUTORS.txt. However this file is not executable

Please do not edit this file manually. It is generated using \`./scripts/generate-contributors-list.sh\`. If a name is misspelled or appearing multiple times: add an entry in \`./.mailmap\`

➜  swift-openapi-generator git:(main) l scripts             
total 72
drwxr-xr-x  11 kyle  staff   352B  6 20 11:38 .
drwxr-xr-x@ 27 kyle  staff   864B  6 20 11:38 ..
-rw-r--r--   1 kyle  staff   1.2K  6 19 23:50 check-for-broken-symlinks.sh
-rw-r--r--   1 kyle  staff   1.3K  6 19 23:50 check-for-docc-warnings.sh
-rw-r--r--   1 kyle  staff   1.3K  6 19 23:50 check-for-unacceptable-language.sh
-rw-r--r--   1 kyle  staff   3.7K  6 20 11:38 check-license-headers.sh
-rw-r--r--   1 kyle  staff   1.9K  6 19 23:50 generate-contributors-list.sh
-rw-r--r--   1 kyle  staff   2.2K  6 19 23:50 run-integration-test.sh
-rw-r--r--   1 kyle  staff   1.5K  6 20 11:38 run-swift-format.sh
-rwxr-xr-x   1 kyle  staff   1.4K  6 19 23:50 soundness.sh
-rw-r--r--   1 kyle  staff   106B  6 19 23:50 unacceptable-language.txt

Since all the scripts file already have #! in the header, we should consider add executable permission to them by chmod +x scripts/*.sh