spec: add missing space in EBNF

[yah01]

Fixes #36520

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Message from Ian Lance Taylor:

Patch Set 1:

(1 comment)

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Message from yah01:

Patch Set 3:

(1 comment)

Patch Set 1:

(1 comment)

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Message from Robert Griesemer:

Patch Set 3:

(1 comment)

LGTM but please up-date the timestamp in the beginning

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Message from yah01:

Patch Set 4:

(1 comment)

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Message from Robert Griesemer:

Patch Set 4: Code-Review+2

Thanks.

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This PR is being closed because golang.org/cl/214821 has been merged.