spec: remove => (alias) operator from Operators and Delimiters section
spec: remove => (alias) operator from Operators and Delimiters section

(Revert of https://go-review.googlesource.com/#/c/32310/)

For #16339.
Fixes #17975.

Change-Id: I36062703c423a81ea1c5b00f4429a4faf00b3782
Reviewed-on: https://go-review.googlesource.com/33365
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

codestation/go,goodlang/good,golang/go,ImJasonH/go,suncycheng/go,polyverse-security/go,ImJasonH/go,goodlang/good,goodlang/good,christopher-henderson/Go,nawawi/go,nawawi/go,linux-on-ibm-z/go,cloudflare/go,ImJasonH/go,cloudflare/go,golang/go,josharian/go,derekmarcotte/go,nawawi/go,Cofyc/go,suncycheng/go,akutz/go,akutz/go,nawawi/go,polyverse-security/go,polyverse-security/go,CAFxX/go,polyverse-security/go,polyverse-security/go,akutz/go,goodlang/good,suncycheng/go,ImJasonH/go,goodlang/good,vsekhar/elastic-go,vsekhar/elastic-go,goodlang/good,akutz/go,linux-on-ibm-z/go,ImJasonH/go,linux-on-ibm-z/go,linux-on-ibm-z/go,nawawi/go,vsekhar/elastic-go,vsekhar/elastic-go,suncycheng/go,golang/go,vsekhar/elastic-go,CAFxX/go,vsekhar/elastic-go,golang/go,CAFxX/go,codestation/go,CAFxX/go,CAFxX/go,linux-on-ibm-z/go,golang/go,derekmarcotte/go,nawawi/go,CAFxX/go,josharian/go,derekmarcotte/go,goodlang/good,goodlang/good,akutz/go,derekmarcotte/go,derekmarcotte/go,cloudflare/go,cloudflare/go,josharian/go,ImJasonH/go,Cofyc/go,polyverse-security/go,codestation/go,josharian/go,ImJasonH/go,vsekhar/elastic-go,suncycheng/go,nawawi/go,josharian/go,golang/go,codestation/go,derekmarcotte/go,codestation/go,josharian/go,vsekhar/elastic-go,codestation/go,akutz/go,cloudflare/go,josharian/go,josharian/go,linux-on-ibm-z/go,Cofyc/go,suncycheng/go,golang/go,golang/go,nawawi/go,ImJasonH/go,linux-on-ibm-z/go,linux-on-ibm-z/go,suncycheng/go,CAFxX/go,derekmarcotte/go,derekmarcotte/go,Cofyc/go,Cofyc/go,codestation/go,cloudflare/go,suncycheng/go,cloudflare/go,akutz/go,Cofyc/go,Cofyc/go,polyverse-security/go,akutz/go,polyverse-security/go,CAFxX/go,Cofyc/go,cloudflare/go,codestation/go