text/template/parse: fix a comment around the assign operator
text/template/parse: fix a comment around the assign operator

Fix a comment that misrepresented the Assign operator (=).

Rename: colon-equals -> equals.

Change-Id: I405b8acfb0bcd1b176a91a95f9bfb61a4e85815f
GitHub-Last-Rev: aec0bf594c63d7b015f88f97f9953ade976817a4
GitHub-Pull-Request: golang/go#26112
Reviewed-on: https://go-review.googlesource.com/121416
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

cloudflare/go,josharian/go,CAFxX/go,akutz/go,nawawi/go,cloudflare/go,cloudflare/go,CAFxX/go,CAFxX/go,nawawi/go,cloudflare/go,nawawi/go,akutz/go,golang/go,golang/go,golang/go,golang/go,josharian/go,josharian/go,CAFxX/go,akutz/go,cloudflare/go,CAFxX/go,cloudflare/go,josharian/go,akutz/go,golang/go,akutz/go,golang/go,CAFxX/go,akutz/go,nawawi/go,josharian/go,cloudflare/go,nawawi/go,josharian/go,golang/go,akutz/go,golang/go,josharian/go,cloudflare/go,josharian/go,CAFxX/go,nawawi/go,akutz/go,nawawi/go,CAFxX/go,nawawi/go