[#712] Remove uses of Parser LetEnv due to redundant constraint

Description

This is to !1094 (merged) what !1107 (merged) was to !1083 (merged)

IOW there are some redundant constraint (in this case on Parser when used with LetEnv) that aren't always detected, but appear and cause issue on some pipelines.

Related issue(s)

Related to #712 (closed)

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