Remove unused packages from Buildkite pipeline

* Chromium isn't used in the unmanaged tablet test
* MySQL Server isn't used anywhere

Signed-off-by: Sergey Stankevich <stankevich@users.noreply.github.com>

Author: stankevich

.buildkite/pipeline.yml

@@ -9,7 +9,7 @@ env:
 steps:
   - name: "Upgrade Test"
     command:
-    - apk add g++ make bash gcompat curl mysql mysql-client libc6-compat
+    - apk add g++ make bash gcompat curl mysql-client libc6-compat
     - wget https://golang.org/dl/$GO_VERSION_FILE
     - tar -C /usr/local -xzf $GO_VERSION_FILE
     - export PATH=$PATH:/usr/local/go/bin:/bin
@@ -28,7 +28,7 @@ steps:
 
   - name: "Backup Restore Test"
     command:
-    - apk add g++ make bash gcompat curl mysql mysql-client libc6-compat
+    - apk add g++ make bash gcompat curl mysql-client libc6-compat
     - wget https://golang.org/dl/$GO_VERSION_FILE
     - tar -C /usr/local -xzf $GO_VERSION_FILE
     - export PATH=$PATH:/usr/local/go/bin:/bin
@@ -47,7 +47,7 @@ steps:
 
   - name: "Backup Schedule Test"
     command:
-      - apk add g++ make bash gcompat curl mysql mysql-client libc6-compat
+      - apk add g++ make bash gcompat curl mysql-client libc6-compat
       - wget https://golang.org/dl/$GO_VERSION_FILE
       - tar -C /usr/local -xzf $GO_VERSION_FILE
       - export PATH=$PATH:/usr/local/go/bin:/bin
@@ -66,7 +66,7 @@ steps:
 
   - name: "VTOrc and VTAdmin Test"
     command:
-    - apk add g++ make bash gcompat curl mysql mysql-client libc6-compat chromium
+    - apk add g++ make bash gcompat curl mysql-client libc6-compat chromium
     - wget https://golang.org/dl/$GO_VERSION_FILE
     - tar -C /usr/local -xzf $GO_VERSION_FILE
     - export PATH=$PATH:/usr/local/go/bin:/bin
@@ -85,7 +85,7 @@ steps:
 
   - name: "Unmanaged Tablet Test"
     command:
-    - apk add g++ make bash gcompat curl mysql mysql-client libc6-compat chromium coreutils
+    - apk add g++ make bash gcompat curl mysql-client libc6-compat coreutils
     - wget https://golang.org/dl/$GO_VERSION_FILE
     - tar -C /usr/local -xzf $GO_VERSION_FILE
     - export PATH=$PATH:/usr/local/go/bin:/bin
@@ -104,7 +104,7 @@ steps:
 
   - name: "HPA Test"
     command:
-    - apk add g++ make bash gcompat curl mysql mysql-client libc6-compat
+    - apk add g++ make bash gcompat curl mysql-client libc6-compat
     - wget https://golang.org/dl/$GO_VERSION_FILE
     - tar -C /usr/local -xzf $GO_VERSION_FILE
     - export PATH=$PATH:/usr/local/go/bin:/bin