remove task-runner dependency

As of #9596, task-runner is no longer used.

Due to how the build system works, task-runner was providing nim-stew,
nim-bearssl and nim-chronos to the project, even though these are also
top-level dependencies - effectively this means there were multiple
versions of these libraries in the source tree and it is not entirely
intuitive which is actually used - adding to the confusion, the
submodule was pinning different versions.

This PR removes task-runner and resets the other dependencies to the
versions in task-runner thus minimising collateral changes.

A duplicate copy of bearssl is also removed.

.gitmodules

@@ -20,9 +20,6 @@
 [submodule "vendor/nimage"]
 	path = vendor/nimage
 	url = https://github.com/Ethosa/nimage/
-[submodule "vendor/bearssl"]
-	path = vendor/bearssl
-	url = https://github.com/status-im/nim-bearssl
 [submodule "vendor/nim-confutils"]
 	path = vendor/nim-confutils
 	url = https://github.com/status-im/nim-confutils.git
@@ -44,9 +41,6 @@
 [submodule "vendor/nim-stew"]
 	path = vendor/nim-stew
 	url = https://github.com/status-im/nim-stew.git
-[submodule "vendor/nim-task-runner"]
-	path = vendor/nim-task-runner
-	url = https://github.com/status-im/nim-task-runner.git
 [submodule "vendor/nimcrypto"]
 	path = vendor/nimcrypto
 	url = https://github.com/cheatfate/nimcrypto.git