Fix typo in `heroku/builder:20` deprecation message #1202

Job	Run time
create (builder-20, amd64)	1m 2s
create (builder-22, amd64)	1m 2s
create (builder-24, amd64)	46s
create (builder-24, arm64)	45s
create (salesforce-functions, amd64)	50s
test-functions (java)	38s
test-functions (javascript)	50s
test-functions (typescript)	52s
test (go, builder-20, amd64)	1m 0s
test (go, builder-22, amd64)	58s
test (go, builder-24, amd64)	49s
test (go, builder-24, arm64)	50s
test (gradle, builder-20, amd64)	1m 41s
test (gradle, builder-22, amd64)	1m 36s
test (gradle, builder-24, amd64)	1m 40s
test (gradle, builder-24, arm64)	1m 49s
test (java, builder-20, amd64)	1m 3s
test (java, builder-22, amd64)	1m 10s
test (java, builder-24, amd64)	1m 3s
test (java, builder-24, arm64)	49s
test (node-js, builder-20, amd64)	54s
test (node-js, builder-22, amd64)	41s
test (node-js, builder-24, amd64)	40s
test (node-js, builder-24, arm64)	44s
test (php, builder-20, amd64)	53s
test (php, builder-22, amd64)	38s
test (php, builder-24, amd64)	35s
test (php, builder-24, arm64)	40s
test (python, builder-20, amd64)	51s
test (python, builder-22, amd64)	47s
test (python, builder-24, amd64)	40s
test (python, builder-24, arm64)	46s
test (ruby, builder-20, amd64)	2m 18s
test (ruby, builder-22, amd64)	2m 11s
test (ruby, builder-24, amd64)	2m 15s
test (ruby, builder-24, arm64)	2m 26s
test (scala, builder-20, amd64)	1m 36s
test (scala, builder-22, amd64)	1m 24s
test (scala, builder-24, amd64)	1m 34s
test (scala, builder-24, arm64)	1m 25s
publish-image	0s
publish-manifest	0s
	45m 11s

Provide feedback