test: Speed up testDefaultMaxEnvelopesConcurrent (#2967)

Set maxCacheItems to 1, so the testDefaultMaxEnvelopesConcurrent test
doesn't need to store 30 envelope items but only 1 for the max envelopes
items logic to run.

Author: philipphofmann

Tests/SentryTests/Helper/SentryFileManagerTests.swift

@@ -244,15 +244,18 @@ class SentryFileManagerTests: XCTestCase {
     }
 
     func testDefaultMaxEnvelopesConcurrent() {
+        let maxCacheItems = 1
+        let sut = fixture.getSut(maxCacheItems: UInt(maxCacheItems))
+        
         let parallelTaskAmount = 5
         let queue = DispatchQueue(label: "testDefaultMaxEnvelopesConcurrent", qos: .userInitiated, attributes: [.concurrent, .initiallyInactive])
 
         let envelopeStoredExpectation = expectation(description: "Envelope stored")
         envelopeStoredExpectation.expectedFulfillmentCount = parallelTaskAmount
         for _ in 0..<parallelTaskAmount {
             queue.async {
-                for _ in 0...(self.fixture.maxCacheItems + 5) {
-                    self.sut.store(TestConstants.envelope)
+                for _ in 0...(maxCacheItems + 5) {
+                    sut.store(TestConstants.envelope)
                 }
                 envelopeStoredExpectation.fulfill()
             }
@@ -262,7 +265,7 @@ class SentryFileManagerTests: XCTestCase {
         wait(for: [envelopeStoredExpectation], timeout: 10)
 
         let events = sut.getAllEnvelopes()
-        XCTAssertEqual(fixture.maxCacheItems, events.count)
+        XCTAssertEqual(maxCacheItems, events.count)
     }
 
     func testMaxEnvelopesSet() {