Remove install-swift from build_swiftsyntax_release preset was added when cherry-picking the commit from master, we don't need this preset on swift-5.1-branch.

Author: shahmishal

utils/build-presets.ini

@@ -1849,8 +1849,6 @@ swiftsyntax
 verbose-build
 skip-swiftsyntax-swiftside
 darwin-install-extract-symbols
-install-swift
-
 
 #===------------------------------------------------------------------------===#
 # Linux corelibs foundation preset
@@ -1861,4 +1859,4 @@ mixin-preset=buildbot_linux
 debug-foundation
 
 [preset: buildbot_linux,foundation=release]
-mixin-preset=buildbot_linux
+mixin-preset=buildbot_linux