fix(upload-api): make text color explicit

[hannahhoward]

Goals

My storacha branded email validation page is rendering body text white and unreadable, cause it's just the browser default. Fix this

Implementation

set text color for body text on storacha branded email validation page to black, rather than relying on browser default color

[seed-deploy[bot]]

View stack outputs

- **pr421-w3infra-BillingDbStack** Name | Value -- | -- customerTableName | pr421-w3infra-customer spaceDiffTableName | pr421-w3infra-space-diff spaceSnapshotTableName | pr421-w3infra-space-snapshot usageTable | pr421-w3infra-usage - **pr421-w3infra-BillingStack** Name | Value -- | -- ApiEndpoint | https://ouvilve0hd.execute-api.us-east-2.amazonaws.com billingCronHandlerURL | https://ippobvsyjztt2mc4nupeh2wfv40rntxf.lambda-url.us-east-2.on.aws/ CustomDomain | https://pr421.billing.web3.storage - **pr421-w3infra-CarparkStack** Name | Value -- | -- BucketName | carpark-pr421-0 Region | us-east-2 - **pr421-w3infra-RoundaboutStack** Name | Value -- | -- ApiEndpoint | https://v9bv1zshyj.execute-api.us-east-2.amazonaws.com CustomDomain | https://pr421.roundabout.web3.storage - **pr421-w3infra-UcanInvocationStack** Name | Value -- | -- invocationBucketName | invocation-store-pr421-0 taskBucketName | task-store-pr421-0 workflowBucketName | workflow-store-pr421-0 - **pr421-w3infra-UploadApiStack** Name | Value -- | -- ApiEndpoints | ["https://e4irgf50m4.execute-api.us-east-2.amazonaws.com","https://osijx2nrj4.execute-api.us-east-2.amazonaws.com"] CustomDomains | ["https://pr421.up.web3.storage","https://pr421.up.storacha.network"] - **pr421-w3infra-BusStack** - **pr421-w3infra-FilecoinStack** - **pr421-w3infra-IndexerStack** - **pr421-w3infra-ReplicatorStack** - **pr421-w3infra-UcanFirehoseStack** - **pr421-w3infra-UploadDbStack**