installDeps.sh: Don't nuke src/node_modules on error

Rationale:
  * Clearing out `src/node_modules` is unlikely to bring future
    success.
  * If there is an error, it's better to leave the filesystem alone so
    that the user can investigate the cause.
  * Deleting the directory on error is a surprising behavior.

src/bin/installDeps.sh

@@ -43,10 +43,7 @@ log "Installing dependencies..."
   { [ -d ep_etherpad-lite ] || ln -sf ../src ep_etherpad-lite; } &&
   cd ep_etherpad-lite &&
   npm ci --no-optional
-) || {
-  rm -rf src/node_modules
-  exit 1
-}
+) || exit 1
 
 # Remove all minified data to force node creating it new
 log "Clearing minified cache..."