Fix Go dependencies

stellar#5084 broke go.mod becaue:

1. go mod tidy wasn't invoked before merging (we should probably enforce this is CI and make sure there are no diffs)
2. It ugraded github.com/creachadair/jrpc2 to 1.1.1 which requires Go 1.21 (breaking the two-Go-release compatibility guarantee we make)

go.mod

@@ -1,6 +1,6 @@
 module github.com/stellar/go
 
-go 1.19
+go 1.20
 
 require (
 	firebase.google.com/go v3.12.0+incompatible
@@ -11,7 +11,7 @@ require (
 	github.com/adjust/goautoneg v0.0.0-20150426214442-d788f35a0315
 	github.com/asaskevich/govalidator v0.0.0-20230301143203-a9d515a09cc2
 	github.com/aws/aws-sdk-go v1.45.26
-	github.com/creachadair/jrpc2 v1.1.1
+	github.com/creachadair/jrpc2 v1.1.0
 	github.com/elazarl/go-bindata-assetfs v1.0.1
 	github.com/getsentry/raven-go v0.2.0
 	github.com/go-chi/chi v4.1.2+incompatible
@@ -61,7 +61,7 @@ require (
 	github.com/andybalholm/brotli v1.0.4 // indirect
 	github.com/certifi/gocertifi v0.0.0-20210507211836-431795d63e8d // indirect
 	github.com/cespare/xxhash/v2 v2.2.0 // indirect
-	github.com/creachadair/mds v0.2.3 // indirect
+	github.com/creachadair/mds v0.0.1 // indirect
 	github.com/fsnotify/fsnotify v1.6.0 // indirect
 	github.com/go-gorp/gorp/v3 v3.1.0 // indirect
 	github.com/gobuffalo/packd v1.0.2 // indirect

go.sum

@@ -95,10 +95,10 @@ github.com/cncf/udpa/go v0.0.0-20191209042840-269d4d468f6f/go.mod h1:M8M6+tZqaGX
 github.com/cncf/udpa/go v0.0.0-20200629203442-efcf912fb354/go.mod h1:WmhPx2Nbnhtbo57+VJT5O0JRkEi1Wbu0z5j0R8u5Hbk=
 github.com/cncf/udpa/go v0.0.0-20201120205902-5459f2c99403/go.mod h1:WmhPx2Nbnhtbo57+VJT5O0JRkEi1Wbu0z5j0R8u5Hbk=
 github.com/cpuguy83/go-md2man/v2 v2.0.2/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
-github.com/creachadair/jrpc2 v1.1.1 h1:xa7p3C5eSvwn/dFwCCmksp+RyQ/ytFY0NYzY7npsoI0=
-github.com/creachadair/jrpc2 v1.1.1/go.mod h1:KajsO5dx7yfcwmuRJb5SHXsCVTzBoq7EsPzu5wxnsc0=
-github.com/creachadair/mds v0.2.3 h1:Svuw/AXrUUMxGHdRyuDsWJ36oFJRprqP8+iI86XzZjM=
-github.com/creachadair/mds v0.2.3/go.mod h1:PmXHgspUECelJVsAgDxWvjblna5BGjPxdEpr7SIEvNs=
+github.com/creachadair/jrpc2 v1.1.0 h1:SgpJf0v1rVCZx68+4APv6dgsTFsIHlpgFD1NlQAWA0A=
+github.com/creachadair/jrpc2 v1.1.0/go.mod h1:5jN7MKwsm8qvgfTsTzLX3JIfidsAkZ1c8DZSQmp+g38=
+github.com/creachadair/mds v0.0.1 h1:2nX6Sww4dXpScx3b6aYjH1n7iuEH715+jj+cKkKw9BY=
+github.com/creachadair/mds v0.0.1/go.mod h1:caBACU+n1Q/rZ252FTzfnG0/H+ZUi+UnIQtEOraMv/g=
 github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=