Fix NullPointerException on resetThrottlesUnconditionally()

[bilyana-gospodinova]

Description:
As a result of the last hedera-app bump to 0.65.1 in #12001 new singleton states were added:

• FunctionReadableSingletonState
• FunctionWritableSingletonState

For the writable one the implementation of putIntoDataSource() and removeFromDataSource() needs to be removed as this introduces a regression and we don't persist any changes in the DB anyway.

Fixes #12055

[lfdt-bot]

🎉 Snyk checks have passed. No issues have been found so far.

✅ security/snyk check is complete. No issues have been found. (View Details)

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
❌ -31.45% (target: -1.00%)	✅ 100.00%

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (e8bbaa4)	36892	33604	91.09%
Head commit (236a209)	60875 (+23983)	36305 (+2701)	59.64% (-31.45%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#12145)	1	1	100.00%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

See your quality gate settings    Change summary preferences