Small fix in image-rotate dockerfile. #2019

Job	Run time
Resolve Modules	7s
GolangCI Lint (./tools/endpoint)	20s
GolangCI Lint (./tools/trace-plotter)	39s
GolangCI Lint (./tools/relay)	37s
GolangCI Lint (./tools/benchmarking_eventing)	31s
GolangCI Lint (./tools/invoker)	29s
GolangCI Lint (./tools/deployer)	32s
GolangCI Lint (./tools/test-client)	34s
GolangCI Lint (./utils/protobuf/helloworld)	32s
GolangCI Lint (./utils/storage/go)	36s
GolangCI Lint (./utils/tracing/integ-tests/client-server/goclient)	31s
GolangCI Lint (./utils/tracing/go)	30s
GolangCI Lint (./benchmarks/chained-function-eventing)	37s
GolangCI Lint (./benchmarks/aes/go)	36s
GolangCI Lint (./benchmarks/spinning/go)	59s
GolangCI Lint (./benchmarks/image-rotate/init)	34s
GolangCI Lint (./benchmarks/image-rotate/go)	41s
GolangCI Lint (./benchmarks/auth/go)	27s
GolangCI Lint (./benchmarks/video-processing/init)	33s
GolangCI Lint (./benchmarks/hotel-app)	43s
GolangCI Lint (./benchmarks/sleeping/go)	36s
GolangCI Lint (./benchmarks/video-analytics)	15s
GolangCI Lint (./benchmarks/fibonacci)	43s
GolangCI Lint (./benchmarks/gg/benchmarks)	34s
GolangCI Lint (./benchmarks/chained-function-serving)	14s
GolangCI Lint (./benchmarks/corral)	53s
	14m 23s

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