build: sqlx update not possible due to performance regressions

Update to 0.6.1 isn't possible right now due to massive increase in
compile time and memory usage. The core build uses 30GB after a few
minutes! With 0.5.13 the build takes less than a minute and < 2GB.

See launchbadge/sqlx#1921
Possible fix with launchbadge/sqlx#1946

Cargo.toml

@@ -26,6 +26,9 @@ regex = "1"
 lazy_static = "1"
 
 [dependencies.sqlx]
+# ATTENTION: 0.6.1 is broken! Compilation takes forever and uses massive amounts of RAM. At 30 GB I killed it...
+# Issue: https://github.com/launchbadge/sqlx/issues/1921
+# Possible PR: https://github.com/launchbadge/sqlx/pull/1946
 version = "0.5"
 default-features = false
 features = [