fix(ci)_: remove workspace and tmp dir

This ensures we do not encounter weird errors like:
```
+ ln -s /home/jenkins/workspace/go_prs_linux_x86_64_main_PR-5907 /home/jenkins/workspace/go_prs_linux_x86_64_main_PR-5907@tmp/go/src/github.com/status-im/status-go
ln: failed to create symbolic link '/home/jenkins/workspace/go_prs_linux_x86_64_main_PR-5907@tmp/go/src/github.com/status-im/status-go': File exists
script returned exit code 1
```

Signed-off-by: Jakub Sokołowski <jakub@status.im>

_assets/ci/Jenkinsfile.android

@@ -85,6 +85,9 @@ pipeline {
   post {
     success { script { github.notifyPR(true) } }
     failure { script { github.notifyPR(false) } }
-    cleanup { sh 'make deep-clean' }
+    cleanup {
+      cleanWs()
+      dir("${env.WORKSPACE}@tmp") { deleteDir() }
+    }
   } // post
 } // pipeline

_assets/ci/Jenkinsfile.ios

@@ -89,6 +89,9 @@ pipeline {
   post {
     success { script { github.notifyPR(true) } }
     failure { script { github.notifyPR(false) } }
-    cleanup { sh 'make deep-clean' }
+    cleanup {
+      cleanWs()
+      dir("${env.WORKSPACE}@tmp") { deleteDir() }
+    }
   } // post
 } // pipeline

_assets/ci/Jenkinsfile.linux

@@ -92,6 +92,9 @@ pipeline {
   post {
     success { script { github.notifyPR(true) } }
     failure { script { github.notifyPR(false) } }
-    cleanup { sh 'make deep-clean' }
+    cleanup {
+      cleanWs()
+      dir("${env.WORKSPACE}@tmp") { deleteDir() }
+    }
   } // post
 } // pipeline

_assets/ci/Jenkinsfile.tests

@@ -238,8 +238,8 @@ pipeline {
       }
     }
     cleanup {
-      dir(env.TMPDIR) { deleteDir() }
-      sh "make git-clean"
+      cleanWs()
+      dir("${env.WORKSPACE}@tmp") { deleteDir() }
     }
   } // post
 } // pipeline
@@ -254,4 +254,4 @@ def getDefaultUnitTestCount() { isNightlyJob() ? '20' : '1' }
 
 def getDefaultTimeout() { isNightlyJob() ? 5*60 : 50 }
 
-def getAmountToKeep() { isNightlyJob() ? '14' : isDevelopJob() ? '10' : '5' }
+def getAmountToKeep() { isNightlyJob() ? '14' : isDevelopJob() ? '10' : '5' }