golang: v↑ go1.14 (1.14.12 -> 1.14.15)

Going Go1.14.12 -> Go1.14.15 brings in fixes to compiler, runtime, standard
library and build security.

https://golang.org/doc/devel/release.html#go1.14.minor

Tested on helloworld SR (by adjusting it to use go1.14 instead of go1.15)

Go1.14.15 is the last Go1.14.x release, because, after Go1.16 was released, Go1.14
becomes end-of-life and will not receive any updates nor fixes for security bugs.

/cc @jerome (for theia which is on go1.14)
/cc @luke (for caddy which is on go1.14)

/cc @tomo, @alain.takoudjou (for galene which is still on EOL go1.13)
/cc @alain.takoudjou (for replication-manager which is still on EOL go1.13)
/cc @alain.takoudjou (for restic which is still on EOL go1.13)

/cc @jerome, @alain.takoudjou (for gitlab which is still on EOL go1.12)
/cc @jerome (for grafana which is still on EOL go1.12)

component/golang/buildout.cfg

@@ -52,8 +52,8 @@ environment-extra =
 
 [golang1.14]
 <= golang-common
-url = https://golang.org/dl/go1.14.12.src.tar.gz
-md5sum = ae124560e0185a82883b57cc9662aa73
+url = https://golang.org/dl/go1.14.15.src.tar.gz
+md5sum = 1065b705a0d330136084f4e1628baf82
 
 # go1.14 needs go1.4 to bootstrap
 environment-extra =