fix(hcl2template): correct 'occured' -> 'occurred' in evaluation diagnostics

[SAY-5]

hcl2template/types.packer_config.go raised two HCL diagnostics with 'An error occured while recursively evaluating ...':

Detail: "An error occured while recursively evaluating locals." + ...   // line 322
Detail: "An error occured while recursively evaluating data "   + ...   // line 431

Both messages are surfaced in packer's diagnostic output to end users when local/data evaluation fails. go build ./hcl2template/... stays clean against current main.

[hashicorp-cla-app]

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