all: upgrade go.mod files to Go 1.16

This enables the narrower "all" pattern described in
https://golang.org/doc/go1.16#all-pattern,
eliminating some otherwise-unnecessary checksums.

For golang/go#36460.

Change-Id: Ia894b1c1d85f8d1317aebb816921e95e7c1da506
Reviewed-on: https://go-review.googlesource.com/c/tools/+/315569
Trust: Bryan C. Mills <[email protected]>
Run-TryBot: Bryan C. Mills <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
gopls-CI: kokoro <[email protected]>
TryBot-Result: Go Bot <[email protected]>

Author: Bryan C. Mills

go.mod

@@ -1,6 +1,6 @@
 module golang.org/x/tools
 
-go 1.12
+go 1.16
 
 require (
 	github.com/yuin/goldmark v1.3.3

gopls/go.mod

@@ -1,6 +1,6 @@
 module golang.org/x/tools/gopls
 
-go 1.12
+go 1.16
 
 require (
 	github.com/google/go-cmp v0.5.5

gopls/go.sum

@@ -12,10 +12,8 @@ github.com/google/safehtml v0.0.2/go.mod h1:L4KWwDsUJdECRAEpZoBn3O64bQaywRscowZj
 github.com/jba/templatecheck v0.5.0 h1:sZwNjXG3xNApuwKmgUWEo2JuxmG0sgNaELl0zwRQ9x8=
 github.com/jba/templatecheck v0.5.0/go.mod h1:/1k7EajoSErFI9GLHAsiIJEaNLt3ALKNw2TV7z2SYv4=
 github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
-github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
-github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/pmezard/go-difflib v0.0.0-20151028094244-d8ed2627bdf0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
@@ -56,7 +54,6 @@ golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1N
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=