Fix YAML syntax issues in DOCUMENTATION

[sivel]

A few of the event_source plugins had invalid DOCUMENTATION due to YAML syntax errors, this PR addresses them by using folded or block scalars.

Generally, if there is a : in the string, with whitespace to the right, YAML will split it as a key/value pair. Using folded or block scalars will resolve the issue as the whole field will be treated as a string.

[github-actions]

Label error. Requires exactly 1 of: bug, enhancement, major, minor, patch, skip-changelog. Found: documentation

[sivel]

fwiw, these were found using the following commands, that kind of abuse the -M argument for ansible-doc:

for F in `ls event_filter/*.py`; do ansible-doc -M event_filter -j "$(basename $F)"; done
for F in `ls event_source/*.py`; do ansible-doc -M event_source -j "$(basename $F)"; done

Since ansible-doc does not yet support directly enumerating the extensions directory, the -M flag sets an additional module directory to look in, and treats the files within as modules.