Increase maxwarns to -1 (#291)

Please see https://github.com/bazelbuild/bazel/issues/25927#issuecomment-2825206105

It's important not to filter out any warnings otherwise the lint warnings are not surfaced and then any attempt to do `-Werror` can fail with what may be observed as spurious (affect other parts of the codebase).

This is maybe a "breaking change" only if someone has enabled `-Werror` and may now see additional errors -- although that was in fact their intention...

Closes #291

COPYBARA_INTEGRATE_REVIEW=https://github.com/bazelbuild/rules_java/pull/291 from fzakaria:patch-1 6938d218c5d8c3640f9c1d98cbf48e55b7f2639d
PiperOrigin-RevId: 819643216
Change-Id: I193e3fca51a56adc6ffa8623ef18729e633623e6

toolchains/default_java_toolchain.bzl

diff --git a/toolchains/default_java_toolchain.bzl b/toolchains/default_java_toolchain.bzl
index f836f8f..5d1d54a 100644
--- a/toolchains/default_java_toolchain.bzl
+++ b/toolchains/default_java_toolchain.bzl
@@ -65,6 +65,9 @@
     "-Xep:LenientFormatStringValidation:OFF",
     "-Xep:ReturnMissingNullable:OFF",
     "-Xep:UseCorrectAssertInTests:OFF",
+    # Please see https://github.com/bazelbuild/bazel/issues/25927#issuecomment-2825206105
+    # we need to make sure not to filter any warnings so that Bazel can trigger them as errors.
+    "-Xmaxwarns -1",
 ]
 
 # If this is changed, the docs for "{,tool_}java_language_version" also