[chore] Simplify the license header

[pellared]

Fixes #4986

Changes

Replace

// Copyright The OpenTelemetry Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

with

// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

Replace

# Copyright The OpenTelemetry Authors
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

with

# Copyright The OpenTelemetry Authors
# SPDX-License-Identifier: Apache-2.0

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.9%. Comparing base (1d1ecbc) to head (5164298).

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #4987     +/-   ##
=======================================
- Coverage   82.9%   82.9%   -0.1%     
=======================================
  Files        238     238             
  Lines      19118   19118             
=======================================
- Hits       15850   15849      -1     
- Misses      2979    2980      +1     
  Partials     289     289             

Files	Coverage Δ
attribute/encoder.go	77.5% <ø> (ø)
attribute/filter.go	100.0% <ø> (ø)
attribute/iterator.go	91.7% <ø> (ø)
attribute/key.go	100.0% <ø> (ø)
attribute/kv.go	91.6% <ø> (ø)
attribute/set.go	80.4% <ø> (ø)
attribute/value.go	91.2% <ø> (ø)
baggage/baggage.go	97.8% <ø> (ø)
baggage/context.go	100.0% <ø> (ø)
bridge/opencensus/config.go	100.0% <ø> (ø)
... and 117 more

... and 106 files with indirect coverage changes