go.mod: bump golang.org/x/net from 0.14.0 to 0.15.0 #297

Job	Run time
CI matrix / Assert PR branch is ahead	9s
Makefile / Assert PR branch is ahead	6s
Makefile / Build codebase using Makefile quick recipe	43s
Makefile / Build codebase using Makefile all recipe	0s
Makefile / Lint codebase using Makefile	0s
CI matrix / Lint codebase (go-ci-oldstable, false)	57s
CI matrix / Lint codebase (go-ci-stable, false)	52s
CI matrix / Run tests (go-ci-oldstable, false)	49s
CI matrix / Build codebase (go-ci-oldstable, false)	43s
CI matrix / Lint codebase (go-ci-unstable, true)	51s
CI matrix / Run tests (go-ci-stable, false)	47s
CI matrix / Build codebase (go-ci-stable, false)	47s
CI matrix / Run tests (go-ci-unstable, true)	53s
CI matrix / Build codebase (go-ci-unstable, true)	43s
CI matrix / Optional Linting / Assert PR branch is ahead	7s
CI matrix / Optional Linting / Lint codebase using optional linters (go-ci-oldstable, true)	52s
CI matrix / Optional Linting / Lint codebase using optional linters (go-ci-stable, true)	50s
CI matrix / Optional Linting / Lint codebase using optional linters (go-ci-unstable, true)	1m 3s
	11m 12s

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