chore(deps): pin dependencies in dockerfile

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
mcr.microsoft.com/devcontainers/base	stage	pinDigest	-> 98a855f
mcr.microsoft.com/devcontainers/javascript-node	final	pinDigest	-> ec1e123
prettier (source)	devDependencies	pin	^3.2.5 -> 3.2.5

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