Don't add comments about API docs previews to PRs (#3791)

Previously we've been adding comments to PRs modifying Solidity
contracts about available previews of the API documentation. As each
push to the PR branch results in one such comment, PRs with a lot of
pushes get quite busy with a lot of the similar comments. In the future
it would be good to modify our commenting mechanism so that it would
just leave one comment per PR and update it on each push. Until we do
that we're turning off the PR commenting, to increase readability.

Ref:
keep-network/tbtc-v2#793
threshold-network/solidity-contracts#165

.github/workflows/contracts-ecdsa-docs.yml

@@ -47,7 +47,7 @@ jobs:
       projectDir: /solidity/ecdsa
       publish: false
       addTOC: false
-      commentPR: true
+      commentPR: false
       exportAsGHArtifacts: true
 
   # This job is needed to avoid a clash of `contracts-docs-publish` jobs for

.github/workflows/contracts-random-beacon-docs.yml

@@ -47,7 +47,7 @@ jobs:
       projectDir: /solidity/random-beacon
       publish: false
       addTOC: false
-      commentPR: true
+      commentPR: false
       exportAsGHArtifacts: true
 
   # This job will be triggered for releases which name starts with